From 6987cd00ad0bd344ab0b3d65472f6ce0fec2cb19 Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Thu, 24 Jul 2025 08:39:13 +0200
Subject: [PATCH 01/22] add taggable doctrine store

---
 .../Message/MessageHeaderRegistry.php         |   2 +
 src/Store/Criteria/TagCriterion.php           |  26 +
 src/Store/Header/TagsHeader.php               |  15 +
 src/Store/TaggableDoctrineDbalStore.php       | 657 ++++++++++++++++++
 src/Store/TaggableDoctrineDbalStoreStream.php | 179 +++++
 .../Store/TaggableDoctrineDbalStoreTest.php   | 594 ++++++++++++++++
 6 files changed, 1473 insertions(+)
 create mode 100644 src/Store/Criteria/TagCriterion.php
 create mode 100644 src/Store/Header/TagsHeader.php
 create mode 100644 src/Store/TaggableDoctrineDbalStore.php
 create mode 100644 src/Store/TaggableDoctrineDbalStoreStream.php
 create mode 100644 tests/Integration/Store/TaggableDoctrineDbalStoreTest.php

diff --git a/src/Metadata/Message/MessageHeaderRegistry.php b/src/Metadata/Message/MessageHeaderRegistry.php
index 75ceeba0..ed15f4d3 100644
--- a/src/Metadata/Message/MessageHeaderRegistry.php
+++ b/src/Metadata/Message/MessageHeaderRegistry.php
@@ -10,6 +10,7 @@
 use Patchlevel\EventSourcing\Store\Header\PlayheadHeader;
 use Patchlevel\EventSourcing\Store\Header\RecordedOnHeader;
 use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
+use Patchlevel\EventSourcing\Store\Header\TagsHeader;
 use Patchlevel\EventSourcing\Store\StreamStartHeader;
 
 use function array_flip;
@@ -83,6 +84,7 @@ public static function createWithInternalHeaders(array $headerNameToClassMap = [
             'newStreamStart' => StreamStartHeader::class,
             'eventId' => EventIdHeader::class,
             'index' => IndexHeader::class,
+            'tags' => TagsHeader::class,
         ];
 
         return new self($headerNameToClassMap + $internalHeaders);
diff --git a/src/Store/Criteria/TagCriterion.php b/src/Store/Criteria/TagCriterion.php
new file mode 100644
index 00000000..957a3f9c
--- /dev/null
+++ b/src/Store/Criteria/TagCriterion.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Store\Criteria;
+
+use InvalidArgumentException;
+
+use function array_unique;
+use function array_values;
+
+final class TagCriterion
+{
+    /** @var list<string> */
+    public readonly array $tags;
+
+    public function __construct(
+        string ...$tags,
+    ) {
+        $this->tags = array_values(array_unique($tags));
+
+        if ($this->tags === []) {
+            throw new InvalidArgumentException('At least one tag must be provided.');
+        }
+    }
+}
diff --git a/src/Store/Header/TagsHeader.php b/src/Store/Header/TagsHeader.php
new file mode 100644
index 00000000..f52a6921
--- /dev/null
+++ b/src/Store/Header/TagsHeader.php
@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Store\Header;
+
+/** @psalm-immutable */
+class TagsHeader
+{
+    /** @param list<string> $tags */
+    public function __construct(
+        public readonly array $tags,
+    ) {
+    }
+}
diff --git a/src/Store/TaggableDoctrineDbalStore.php b/src/Store/TaggableDoctrineDbalStore.php
new file mode 100644
index 00000000..3605f4e6
--- /dev/null
+++ b/src/Store/TaggableDoctrineDbalStore.php
@@ -0,0 +1,657 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Store;
+
+use Closure;
+use Doctrine\DBAL\ArrayParameterType;
+use Doctrine\DBAL\Connection;
+use Doctrine\DBAL\Exception\UniqueConstraintViolationException;
+use Doctrine\DBAL\Platforms\MariaDBPlatform;
+use Doctrine\DBAL\Platforms\MySQLPlatform;
+use Doctrine\DBAL\Platforms\PostgreSQLPlatform;
+use Doctrine\DBAL\Platforms\SQLitePlatform;
+use Doctrine\DBAL\Query\QueryBuilder;
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\DBAL\Types\Type;
+use Doctrine\DBAL\Types\Types;
+use Patchlevel\EventSourcing\Clock\SystemClock;
+use Patchlevel\EventSourcing\Message\HeaderNotFound;
+use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Message\Serializer\DefaultHeadersSerializer;
+use Patchlevel\EventSourcing\Message\Serializer\HeadersSerializer;
+use Patchlevel\EventSourcing\Schema\DoctrineSchemaConfigurator;
+use Patchlevel\EventSourcing\Serializer\EventSerializer;
+use Patchlevel\EventSourcing\Store\Criteria\ArchivedCriterion;
+use Patchlevel\EventSourcing\Store\Criteria\Criteria;
+use Patchlevel\EventSourcing\Store\Criteria\EventIdCriterion;
+use Patchlevel\EventSourcing\Store\Criteria\EventsCriterion;
+use Patchlevel\EventSourcing\Store\Criteria\FromIndexCriterion;
+use Patchlevel\EventSourcing\Store\Criteria\FromPlayheadCriterion;
+use Patchlevel\EventSourcing\Store\Criteria\StreamCriterion;
+use Patchlevel\EventSourcing\Store\Criteria\TagCriterion;
+use Patchlevel\EventSourcing\Store\Criteria\ToIndexCriterion;
+use Patchlevel\EventSourcing\Store\Criteria\ToPlayheadCriterion;
+use Patchlevel\EventSourcing\Store\Header\EventIdHeader;
+use Patchlevel\EventSourcing\Store\Header\IndexHeader;
+use Patchlevel\EventSourcing\Store\Header\PlayheadHeader;
+use Patchlevel\EventSourcing\Store\Header\RecordedOnHeader;
+use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
+use Patchlevel\EventSourcing\Store\Header\TagsHeader;
+use PDO;
+use Psr\Clock\ClockInterface;
+use Ramsey\Uuid\Uuid;
+
+use function array_fill;
+use function array_filter;
+use function array_merge;
+use function array_values;
+use function class_exists;
+use function count;
+use function explode;
+use function floor;
+use function implode;
+use function in_array;
+use function is_int;
+use function is_string;
+use function sprintf;
+use function str_contains;
+use function str_replace;
+
+/** @experimental */
+final class TaggableDoctrineDbalStore implements StreamStore, SubscriptionStore, DoctrineSchemaConfigurator
+{
+    /**
+     * PostgreSQL has a limit of 65535 parameters in a single query.
+     */
+    private const MAX_UNSIGNED_SMALL_INT = 65_535;
+
+    /**
+     * Default lock id for advisory lock.
+     */
+    private const DEFAULT_LOCK_ID = 133742;
+
+    private readonly HeadersSerializer $headersSerializer;
+
+    private readonly ClockInterface $clock;
+
+    /** @var array{table_name: string, locking: bool, lock_id: int, lock_timeout: int, keep_index: bool} */
+    private readonly array $config;
+
+    private bool $hasLock = false;
+
+    private readonly bool $isMysql;
+
+    private readonly bool $isMariaDb;
+
+    private readonly bool $isPostgres;
+
+    private readonly bool $isSQLite;
+
+    /** @param array{table_name?: string, locking?: bool, lock_id?: int, lock_timeout?: int, keep_index?: bool} $config */
+    public function __construct(
+        private readonly Connection $connection,
+        private readonly EventSerializer $eventSerializer,
+        HeadersSerializer|null $headersSerializer = null,
+        ClockInterface|null $clock = null,
+        array $config = [],
+    ) {
+        $this->headersSerializer = $headersSerializer ?? DefaultHeadersSerializer::createDefault();
+        $this->clock = $clock ?? new SystemClock();
+
+        $this->config = array_merge([
+            'table_name' => 'event_store',
+            'locking' => true,
+            'lock_id' => self::DEFAULT_LOCK_ID,
+            'lock_timeout' => -1,
+            'keep_index' => false,
+        ], $config);
+
+        $platform = $this->connection->getDatabasePlatform();
+
+        $this->isMysql = $platform instanceof MySQLPlatform;
+        $this->isMariaDb = $platform instanceof MariaDBPlatform;
+        $this->isPostgres = $platform instanceof PostgreSQLPlatform;
+        $this->isSQLite = $platform instanceof SQLitePlatform;
+    }
+
+    public function load(
+        Criteria|null $criteria = null,
+        int|null $limit = null,
+        int|null $offset = null,
+        bool $backwards = false,
+    ): TaggableDoctrineDbalStoreStream {
+        $builder = $this->connection->createQueryBuilder()
+            ->select('*')
+            ->from($this->config['table_name'])
+            ->orderBy('id', $backwards ? 'DESC' : 'ASC');
+
+        $this->applyCriteria($builder, $criteria ?? new Criteria());
+
+        $builder->setMaxResults($limit);
+        $builder->setFirstResult($offset ?? 0);
+
+        return new TaggableDoctrineDbalStoreStream(
+            $this->connection->executeQuery(
+                $builder->getSQL(),
+                $builder->getParameters(),
+                $builder->getParameterTypes(),
+            ),
+            $this->eventSerializer,
+            $this->headersSerializer,
+            $this->connection->getDatabasePlatform(),
+        );
+    }
+
+    public function count(Criteria|null $criteria = null): int
+    {
+        $builder = $this->connection->createQueryBuilder()
+            ->select('COUNT(*)')
+            ->from($this->config['table_name']);
+
+        $this->applyCriteria($builder, $criteria ?? new Criteria());
+
+        $result = $this->connection->fetchOne(
+            $builder->getSQL(),
+            $builder->getParameters(),
+            $builder->getParameterTypes(),
+        );
+
+        if (!is_int($result) && !is_string($result)) {
+            throw new WrongQueryResult();
+        }
+
+        return (int)$result;
+    }
+
+    private function applyCriteria(QueryBuilder $builder, Criteria $criteria): void
+    {
+        $criteriaList = $criteria->all();
+
+        foreach ($criteriaList as $criterion) {
+            switch ($criterion::class) {
+                case StreamCriterion::class:
+                    if ($criterion->all()) {
+                        break;
+                    }
+
+                    $streamFilters = [];
+
+                    foreach ($criterion->streamName as $index => $streamName) {
+                        if (str_contains($streamName, '*')) {
+                            $streamFilters[] = 'stream LIKE :stream_' . $index;
+                            $builder->setParameter('stream_' . $index, str_replace('*', '%', $streamName));
+                        } else {
+                            $streamFilters[] = 'stream = :stream_' . $index;
+                            $builder->setParameter('stream_' . $index, $streamName);
+                        }
+                    }
+
+                    if ($streamFilters === []) {
+                        break;
+                    }
+
+                    $builder->andWhere($builder->expr()->or(...$streamFilters));
+
+                    break;
+                case FromPlayheadCriterion::class:
+                    $builder->andWhere('playhead > :from_playhead');
+                    $builder->setParameter('from_playhead', $criterion->fromPlayhead, Types::INTEGER);
+                    break;
+                case ToPlayheadCriterion::class:
+                    $builder->andWhere('playhead < :to_playhead');
+                    $builder->setParameter('to_playhead', $criterion->toPlayhead, Types::INTEGER);
+                    break;
+                case ArchivedCriterion::class:
+                    $builder->andWhere('archived = :archived');
+                    $builder->setParameter('archived', $criterion->archived, Types::BOOLEAN);
+                    break;
+                case FromIndexCriterion::class:
+                    $builder->andWhere('id > :from_index');
+                    $builder->setParameter('from_index', $criterion->fromIndex, Types::INTEGER);
+                    break;
+                case ToIndexCriterion::class:
+                    $builder->andWhere('id < :to_index');
+                    $builder->setParameter('to_index', $criterion->toIndex, Types::INTEGER);
+                    break;
+                case EventsCriterion::class:
+                    $builder->andWhere('event_name IN (:events)');
+                    $builder->setParameter('events', $criterion->events, ArrayParameterType::STRING);
+                    break;
+                case EventIdCriterion::class:
+                    $builder->andWhere('event_id = :event_id');
+                    $builder->setParameter('event_id', $criterion->eventId, ArrayParameterType::STRING);
+                    break;
+                case TagCriterion::class:
+                    if ($this->isSQLite) {
+                        $builder->andWhere('NOT EXISTS(SELECT value FROM JSON_EACH(:tags) WHERE value NOT IN (SELECT value FROM JSON_EACH(tags)))');
+                    } elseif ($this->isPostgres) {
+                        $builder->andWhere('tags @> :tags::jsonb');
+                    } elseif ($this->isMysql || $this->isMariaDb) {
+                        $builder->andWhere('JSON_CONTAINS(tags, :tags)');
+                    } else {
+                        throw new UnsupportedCriterion($criterion::class);
+                    }
+
+                    $builder->setParameter('tags', $criterion->tags, Types::JSON);
+                    break;
+                default:
+                    throw new UnsupportedCriterion($criterion::class);
+            }
+        }
+    }
+
+    public function save(Message ...$messages): void
+    {
+        if ($messages === []) {
+            return;
+        }
+
+        $this->transactional(
+            function () use ($messages): void {
+                $booleanType = Type::getType(Types::BOOLEAN);
+                $dateTimeType = Type::getType(Types::DATETIMETZ_IMMUTABLE);
+                $jsonType = Type::getType(Types::JSON);
+
+                $columns = [
+                    'stream',
+                    'playhead',
+                    'event_id',
+                    'event_name',
+                    'event_payload',
+                    'tags',
+                    'recorded_on',
+                    'archived',
+                    'custom_headers',
+                ];
+
+                if ($this->config['keep_index']) {
+                    $columns[] = 'id';
+                }
+
+                $columnsLength = count($columns);
+                $batchSize = (int)floor(self::MAX_UNSIGNED_SMALL_INT / $columnsLength);
+                $placeholder = implode(', ', array_fill(0, $columnsLength, '?'));
+
+                $parameters = [];
+                $placeholders = [];
+                /** @var array<int<0, max>, Type> $types */
+                $types = [];
+                $position = 0;
+                foreach ($messages as $message) {
+                    /** @var int<0, max> $offset */
+                    $offset = $position * $columnsLength;
+                    $placeholders[] = $placeholder;
+
+                    $data = $this->eventSerializer->serialize($message->event());
+
+                    try {
+                        $streamName = $message->header(StreamNameHeader::class)->streamName;
+                        $parameters[] = $streamName;
+                    } catch (HeaderNotFound $e) {
+                        throw new MissingDataForStorage($e->name, $e);
+                    }
+
+                    if ($message->hasHeader(PlayheadHeader::class)) {
+                        $parameters[] = $message->header(PlayheadHeader::class)->playhead;
+                    } else {
+                        $parameters[] = null;
+                    }
+
+                    if ($message->hasHeader(EventIdHeader::class)) {
+                        $eventId = $message->header(EventIdHeader::class)->eventId;
+                    } else {
+                        $eventId = Uuid::uuid7()->toString();
+                    }
+
+                    $parameters[] = $eventId;
+                    $parameters[] = $data->name;
+                    $parameters[] = $data->payload;
+
+                    if ($message->hasHeader(TagsHeader::class)) {
+                        $parameters[] = $message->header(TagsHeader::class)->tags;
+                    } else {
+                        $parameters[] = [];
+                    }
+
+                    $types[$offset + 5] = $jsonType;
+
+                    if ($message->hasHeader(RecordedOnHeader::class)) {
+                        $parameters[] = $message->header(RecordedOnHeader::class)->recordedOn;
+                    } else {
+                        $parameters[] = $this->clock->now();
+                    }
+
+                    $types[$offset + 6] = $dateTimeType;
+
+                    $parameters[] = $message->hasHeader(ArchivedHeader::class);
+                    $types[$offset + 7] = $booleanType;
+
+                    $parameters[] = $this->headersSerializer->serialize($this->getCustomHeaders($message));
+
+                    if ($this->config['keep_index']) {
+                        try {
+                            $parameters[] = $message->header(IndexHeader::class)->index;
+                        } catch (HeaderNotFound $e) {
+                            throw new MissingDataForStorage($e->name, $e);
+                        }
+                    }
+
+                    $position++;
+
+                    if ($position !== $batchSize) {
+                        continue;
+                    }
+
+                    $this->executeSave($columns, $placeholders, $parameters, $types, $this->connection);
+
+                    $parameters = [];
+                    $placeholders = [];
+                    $types = [];
+
+                    $position = 0;
+                }
+
+                if ($position === 0) {
+                    return;
+                }
+
+                $this->executeSave($columns, $placeholders, $parameters, $types, $this->connection);
+
+                if (!$this->config['keep_index'] || !$this->isPostgres) {
+                    return;
+                }
+
+                $this->connection->executeStatement(
+                    sprintf(
+                        "SELECT setval('%s', (SELECT MAX(id) FROM %s));",
+                        sprintf('%s_id_seq', $this->config['table_name']),
+                        $this->config['table_name'],
+                    ),
+                );
+            },
+        );
+    }
+
+    /**
+     * @param Closure():ClosureReturn $function
+     *
+     * @template ClosureReturn
+     */
+    public function transactional(Closure $function): void
+    {
+        if ($this->hasLock || !$this->config['locking']) {
+            $this->connection->transactional($function);
+        } else {
+            $this->connection->transactional(function () use ($function): void {
+                $this->lock();
+                try {
+                    $function();
+                } finally {
+                    $this->unlock();
+                }
+            });
+        }
+    }
+
+    /** @return list<string> */
+    public function streams(): array
+    {
+        $builder = $this->connection->createQueryBuilder()
+            ->select('stream')
+            ->distinct()
+            ->from($this->config['table_name'])
+            ->orderBy('stream');
+
+        /** @var list<string> $streams */
+        $streams = $builder->fetchFirstColumn();
+
+        return $streams;
+    }
+
+    public function remove(Criteria|null $criteria = null): void
+    {
+        $builder = $this->connection->createQueryBuilder();
+
+        $builder->delete($this->config['table_name']);
+        $this->applyCriteria($builder, $criteria ?? new Criteria());
+
+        $builder->executeStatement();
+    }
+
+    public function archive(Criteria|null $criteria = null): void
+    {
+        $builder = $this->connection->createQueryBuilder();
+
+        $builder->update($this->config['table_name']);
+
+        $this->applyCriteria($builder, $criteria ?? new Criteria());
+
+        $builder
+            ->set('archived', ':value')
+            ->setParameter('value', true, Types::BOOLEAN);
+
+        $builder->executeStatement();
+    }
+
+    public function configureSchema(Schema $schema, Connection $connection): void
+    {
+        if ($this->connection !== $connection) {
+            return;
+        }
+
+        $table = $schema->createTable($this->config['table_name']);
+
+        $table->addColumn('id', Types::BIGINT)
+            ->setAutoincrement(true);
+        $table->addColumn('stream', Types::STRING)
+            ->setLength(255)
+            ->setNotnull(true);
+        $table->addColumn('playhead', Types::INTEGER)
+            ->setNotnull(false);
+        $table->addColumn('event_id', Types::STRING)
+            ->setLength(255)
+            ->setNotnull(true);
+        $table->addColumn('event_name', Types::STRING)
+            ->setLength(255)
+            ->setNotnull(true);
+        $table->addColumn('event_payload', Types::JSON)
+            ->setNotnull(true);
+        $table->addColumn('recorded_on', Types::DATETIMETZ_IMMUTABLE)
+            ->setNotnull(true);
+        $table->addColumn('archived', Types::BOOLEAN)
+            ->setNotnull(true)
+            ->setDefault(false);
+        $table->addColumn('tags', Types::JSON)
+            ->setPlatformOptions($this->isPostgres ? ['jsonb' => true] : [])
+            ->setLength(255)
+            ->setNotnull(false);
+
+        $table->addColumn('custom_headers', Types::JSON)
+            ->setNotnull(true);
+
+        $table->setPrimaryKey(['id']);
+        $table->addUniqueIndex(['event_id']);
+        $table->addUniqueIndex(['stream', 'playhead']);
+        $table->addIndex(['stream', 'playhead', 'archived']);
+    }
+
+    /** @return list<object> */
+    private function getCustomHeaders(Message $message): array
+    {
+        $filteredHeaders = [
+            IndexHeader::class,
+            StreamNameHeader::class,
+            EventIdHeader::class,
+            PlayheadHeader::class,
+            RecordedOnHeader::class,
+            ArchivedHeader::class,
+        ];
+
+        return array_values(
+            array_filter(
+                $message->headers(),
+                static fn (object $header) => !in_array($header::class, $filteredHeaders, true),
+            ),
+        );
+    }
+
+    public function supportSubscription(): bool
+    {
+        return $this->isPostgres && class_exists(PDO::class);
+    }
+
+    public function wait(int $timeoutMilliseconds): void
+    {
+        if (!$this->supportSubscription()) {
+            return;
+        }
+
+        $this->connection->executeStatement(sprintf('LISTEN "%s"', $this->config['table_name']));
+
+        /** @var PDO $nativeConnection */
+        $nativeConnection = $this->connection->getNativeConnection();
+
+        $nativeConnection->pgsqlGetNotify(PDO::FETCH_ASSOC, $timeoutMilliseconds);
+    }
+
+    public function setupSubscription(): void
+    {
+        if (!$this->supportSubscription()) {
+            return;
+        }
+
+        $functionName = $this->createTriggerFunctionName();
+
+        $this->connection->executeStatement(sprintf(
+            <<<'SQL'
+                CREATE OR REPLACE FUNCTION %1$s() RETURNS TRIGGER AS $$
+                    BEGIN
+                        PERFORM pg_notify('%2$s', NEW.stream::text);
+                        RETURN NEW;
+                    END;
+                $$ LANGUAGE plpgsql;
+                SQL,
+            $functionName,
+            $this->config['table_name'],
+        ));
+
+        $this->connection->executeStatement(sprintf(
+            'DROP TRIGGER IF EXISTS notify_trigger ON %s;',
+            $this->config['table_name'],
+        ));
+        $this->connection->executeStatement(sprintf(
+            'CREATE TRIGGER notify_trigger AFTER INSERT OR UPDATE ON %1$s FOR EACH ROW EXECUTE PROCEDURE %2$s();',
+            $this->config['table_name'],
+            $functionName,
+        ));
+    }
+
+    public function connection(): Connection
+    {
+        return $this->connection;
+    }
+
+    private function createTriggerFunctionName(): string
+    {
+        $tableConfig = explode('.', $this->config['table_name']);
+
+        if (count($tableConfig) === 1) {
+            return sprintf('notify_%1$s', $tableConfig[0]);
+        }
+
+        return sprintf('%1$s.notify_%2$s', $tableConfig[0], $tableConfig[1]);
+    }
+
+    /**
+     * @param array<string>               $columns
+     * @param array<string>               $placeholders
+     * @param list<mixed>                 $parameters
+     * @param array<0|positive-int, Type> $types
+     */
+    private function executeSave(
+        array $columns,
+        array $placeholders,
+        array $parameters,
+        array $types,
+        Connection $connection,
+    ): void {
+        $query = sprintf(
+            "INSERT INTO %s (%s) VALUES\n(%s)",
+            $this->config['table_name'],
+            implode(', ', $columns),
+            implode("),\n(", $placeholders),
+        );
+
+        try {
+            $connection->executeStatement($query, $parameters, $types);
+        } catch (UniqueConstraintViolationException $e) {
+            throw new UniqueConstraintViolation($e);
+        }
+    }
+
+    private function lock(): void
+    {
+        $this->hasLock = true;
+
+        if ($this->isPostgres) {
+            $this->connection->executeStatement(
+                sprintf(
+                    'SELECT pg_advisory_xact_lock(%s)',
+                    $this->config['lock_id'],
+                ),
+            );
+
+            return;
+        }
+
+        if ($this->isMariaDb || $this->isMysql) {
+            $this->connection->fetchAllAssociative(
+                sprintf(
+                    'SELECT GET_LOCK("%s", %d)',
+                    $this->config['lock_id'],
+                    $this->config['lock_timeout'],
+                ),
+            );
+
+            return;
+        }
+
+        if ($this->isSQLite) {
+            return; // sql locking is not needed because of file locking
+        }
+
+        throw new LockingNotImplemented(
+            $this->connection->getDatabasePlatform()::class,
+        );
+    }
+
+    private function unlock(): void
+    {
+        $this->hasLock = false;
+
+        if ($this->isPostgres) {
+            return; // lock is released automatically after transaction
+        }
+
+        if ($this->isMariaDb || $this->isMysql) {
+            $this->connection->fetchAllAssociative(
+                sprintf(
+                    'SELECT RELEASE_LOCK("%s")',
+                    $this->config['lock_id'],
+                ),
+            );
+
+            return;
+        }
+
+        if ($this->isSQLite) {
+            return; // sql locking is not needed because of file locking
+        }
+
+        throw new LockingNotImplemented(
+            $this->connection->getDatabasePlatform()::class,
+        );
+    }
+}
diff --git a/src/Store/TaggableDoctrineDbalStoreStream.php b/src/Store/TaggableDoctrineDbalStoreStream.php
new file mode 100644
index 00000000..fc9affb3
--- /dev/null
+++ b/src/Store/TaggableDoctrineDbalStoreStream.php
@@ -0,0 +1,179 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Store;
+
+use Doctrine\DBAL\Platforms\AbstractPlatform;
+use Doctrine\DBAL\Result;
+use Doctrine\DBAL\Types\DateTimeTzImmutableType;
+use Doctrine\DBAL\Types\Type;
+use Doctrine\DBAL\Types\Types;
+use Generator;
+use IteratorAggregate;
+use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Message\Serializer\HeadersSerializer;
+use Patchlevel\EventSourcing\Serializer\EventSerializer;
+use Patchlevel\EventSourcing\Serializer\SerializedEvent;
+use Patchlevel\EventSourcing\Store\Header\EventIdHeader;
+use Patchlevel\EventSourcing\Store\Header\IndexHeader;
+use Patchlevel\EventSourcing\Store\Header\PlayheadHeader;
+use Patchlevel\EventSourcing\Store\Header\RecordedOnHeader;
+use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
+use Patchlevel\EventSourcing\Store\Header\TagsHeader;
+use Traversable;
+
+use function json_decode;
+
+use const JSON_THROW_ON_ERROR;
+
+/**
+ * @experimental
+ * @implements IteratorAggregate<Message>
+ */
+final class TaggableDoctrineDbalStoreStream implements Stream, IteratorAggregate
+{
+    private Result|null $result;
+
+    /** @var Generator<Message> */
+    private Generator|null $generator;
+
+    /** @var positive-int|0|null */
+    private int|null $position;
+
+    /** @var positive-int|null */
+    private int|null $index;
+
+    public function __construct(
+        Result $result,
+        EventSerializer $eventSerializer,
+        HeadersSerializer $headersSerializer,
+        AbstractPlatform $platform,
+    ) {
+        $this->result = $result;
+        $this->generator = $this->buildGenerator($result, $eventSerializer, $headersSerializer, $platform);
+        $this->position = null;
+        $this->index = null;
+    }
+
+    public function close(): void
+    {
+        $this->result?->free();
+
+        $this->result = null;
+        $this->generator = null;
+    }
+
+    public function next(): void
+    {
+        $this->assertNotClosed();
+
+        $this->generator->next();
+    }
+
+    public function end(): bool
+    {
+        $this->assertNotClosed();
+
+        return !$this->generator->valid();
+    }
+
+    public function current(): Message|null
+    {
+        $this->assertNotClosed();
+
+        return $this->generator->current() ?: null;
+    }
+
+    /** @return positive-int|0|null */
+    public function position(): int|null
+    {
+        $this->assertNotClosed();
+
+        if ($this->position === null) {
+            $this->generator->key();
+        }
+
+        return $this->position;
+    }
+
+    /** @return positive-int|null */
+    public function index(): int|null
+    {
+        $this->assertNotClosed();
+
+        if ($this->index === null) {
+            $this->generator->key();
+        }
+
+        return $this->index;
+    }
+
+    /** @return Traversable<Message> */
+    public function getIterator(): Traversable
+    {
+        $this->assertNotClosed();
+
+        return $this->generator;
+    }
+
+    /** @return Generator<Message> */
+    private function buildGenerator(
+        Result $result,
+        EventSerializer $eventSerializer,
+        HeadersSerializer $headersSerializer,
+        AbstractPlatform $platform,
+    ): Generator {
+        /** @var DateTimeTzImmutableType $dateTimeType */
+        $dateTimeType = Type::getType(Types::DATETIMETZ_IMMUTABLE);
+
+        /** @var array{id: positive-int, stream: string, playhead: int|string|null, event_id: string, event_name: string, event_payload: string, tags: string, recorded_on: string, archived: int|string, custom_headers: string} $data */
+        foreach ($result->iterateAssociative() as $data) {
+            if ($this->position === null) {
+                $this->position = 0;
+            } else {
+                ++$this->position;
+            }
+
+            $this->index = $data['id'];
+            $event = $eventSerializer->deserialize(new SerializedEvent($data['event_name'], $data['event_payload']));
+
+            $message = Message::create($event)
+                ->withHeader(new IndexHeader($data['id']))
+                ->withHeader(new StreamNameHeader($data['stream']))
+                ->withHeader(new RecordedOnHeader($dateTimeType->convertToPHPValue($data['recorded_on'], $platform)))
+                ->withHeader(new EventIdHeader($data['event_id']));
+
+            if ($data['playhead'] !== null) {
+                $message = $message->withHeader(new PlayheadHeader((int)$data['playhead']));
+            }
+
+            if ($data['archived']) {
+                $message = $message->withHeader(new ArchivedHeader());
+            }
+
+            if ($data['tags'] !== '[]') {
+                $message = $message->withHeader(
+                    new TagsHeader(
+                        json_decode($data['tags'], true, 512, JSON_THROW_ON_ERROR),
+                    ),
+                );
+            }
+
+            $customHeaders = $headersSerializer->deserialize($data['custom_headers']);
+
+            yield $message->withHeaders($customHeaders);
+        }
+    }
+
+    /**
+     * @psalm-assert !null $this->result
+     * @psalm-assert !null $this->generator
+     */
+    private function assertNotClosed(): void
+    {
+        if ($this->result === null || $this->generator === null) {
+            throw new StreamClosed();
+        }
+    }
+}
diff --git a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
new file mode 100644
index 00000000..c8b50387
--- /dev/null
+++ b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
@@ -0,0 +1,594 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\Store;
+
+use DateTimeImmutable;
+use Doctrine\DBAL\Connection;
+use Patchlevel\EventSourcing\Clock\FrozenClock;
+use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Schema\DoctrineSchemaDirector;
+use Patchlevel\EventSourcing\Serializer\DefaultEventSerializer;
+use Patchlevel\EventSourcing\Store\Criteria\Criteria;
+use Patchlevel\EventSourcing\Store\Criteria\StreamCriterion;
+use Patchlevel\EventSourcing\Store\Criteria\TagCriterion;
+use Patchlevel\EventSourcing\Store\Criteria\ToPlayheadCriterion;
+use Patchlevel\EventSourcing\Store\Header\EventIdHeader;
+use Patchlevel\EventSourcing\Store\Header\IndexHeader;
+use Patchlevel\EventSourcing\Store\Header\PlayheadHeader;
+use Patchlevel\EventSourcing\Store\Header\RecordedOnHeader;
+use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
+use Patchlevel\EventSourcing\Store\Header\TagsHeader;
+use Patchlevel\EventSourcing\Store\StreamStore;
+use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
+use Patchlevel\EventSourcing\Store\UniqueConstraintViolation;
+use Patchlevel\EventSourcing\Tests\DbalManager;
+use Patchlevel\EventSourcing\Tests\Integration\Store\Events\ExternEvent;
+use Patchlevel\EventSourcing\Tests\Integration\Store\Events\ProfileCreated;
+use PHPUnit\Framework\Attributes\CoversNothing;
+use PHPUnit\Framework\TestCase;
+use Psr\Clock\ClockInterface;
+
+use function iterator_to_array;
+use function json_decode;
+use function sprintf;
+
+#[CoversNothing]
+final class TaggableDoctrineDbalStoreTest extends TestCase
+{
+    private Connection $connection;
+    private StreamStore $store;
+
+    private ClockInterface $clock;
+
+    public function setUp(): void
+    {
+        $this->connection = DbalManager::createConnection();
+
+        $this->clock = new FrozenClock(new DateTimeImmutable('2020-01-01 00:00:00'));
+
+        $this->store = new TaggableDoctrineDbalStore(
+            $this->connection,
+            DefaultEventSerializer::createFromPaths([__DIR__ . '/Events']),
+            clock: $this->clock,
+        );
+
+        $schemaDirector = new DoctrineSchemaDirector(
+            $this->connection,
+            $this->store,
+        );
+
+        $schemaDirector->create();
+    }
+
+    public function tearDown(): void
+    {
+        $this->connection->close();
+    }
+
+    public function testSave(): void
+    {
+        $profileId = ProfileId::generate();
+
+        $messages = [
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(1))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00'))),
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(2))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-02 00:00:00'))),
+        ];
+
+        $this->store->save(...$messages);
+
+        /** @var list<array<string, string>> $result */
+        $result = $this->connection->fetchAllAssociative('SELECT * FROM event_store');
+
+        self::assertCount(2, $result);
+
+        $result1 = $result[0];
+
+        self::assertEquals(sprintf('profile-%s', $profileId->toString()), $result1['stream']);
+        self::assertEquals('1', $result1['playhead']);
+        self::assertStringContainsString('2020-01-01 00:00:00', $result1['recorded_on']);
+        self::assertEquals('profile.created', $result1['event_name']);
+        self::assertEquals(
+            ['profileId' => $profileId->toString(), 'name' => 'test'],
+            json_decode($result1['event_payload'], true),
+        );
+
+        $result2 = $result[1];
+
+        self::assertEquals(sprintf('profile-%s', $profileId->toString()), $result2['stream']);
+        self::assertEquals('2', $result2['playhead']);
+        self::assertStringContainsString('2020-01-02 00:00:00', $result2['recorded_on']);
+        self::assertEquals('profile.created', $result2['event_name']);
+        self::assertEquals(
+            ['profileId' => $profileId->toString(), 'name' => 'test'],
+            json_decode($result2['event_payload'], true),
+        );
+    }
+
+    public function testSaveWithIndex(): void
+    {
+        $profileId = ProfileId::generate();
+
+        $messages = [
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(1))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+                ->withHeader(new IndexHeader(1)),
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(2))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-02 00:00:00')))
+                ->withHeader(new IndexHeader(42)),
+        ];
+
+        $store = new TaggableDoctrineDbalStore(
+            $this->connection,
+            DefaultEventSerializer::createFromPaths([__DIR__ . '/Events']),
+            clock: $this->clock,
+            config: ['keep_index' => true],
+        );
+
+        $store->save(...$messages);
+
+        $store = new TaggableDoctrineDbalStore(
+            $this->connection,
+            DefaultEventSerializer::createFromPaths([__DIR__ . '/Events']),
+            clock: $this->clock,
+        );
+
+        $store->save(
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(3))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-02 00:00:00'))),
+        );
+
+        /** @var list<array<string, string>> $result */
+        $result = $this->connection->fetchAllAssociative('SELECT * FROM event_store');
+
+        self::assertCount(3, $result);
+
+        $result1 = $result[0];
+
+        self::assertEquals(1, $result1['id']);
+        self::assertEquals(sprintf('profile-%s', $profileId->toString()), $result1['stream']);
+        self::assertEquals('1', $result1['playhead']);
+        self::assertStringContainsString('2020-01-01 00:00:00', $result1['recorded_on']);
+        self::assertEquals('profile.created', $result1['event_name']);
+        self::assertEquals(
+            ['profileId' => $profileId->toString(), 'name' => 'test'],
+            json_decode($result1['event_payload'], true),
+        );
+
+        $result2 = $result[1];
+
+        self::assertEquals(42, $result2['id']);
+        self::assertEquals(sprintf('profile-%s', $profileId->toString()), $result2['stream']);
+        self::assertEquals('2', $result2['playhead']);
+        self::assertStringContainsString('2020-01-02 00:00:00', $result2['recorded_on']);
+        self::assertEquals('profile.created', $result2['event_name']);
+        self::assertEquals(
+            ['profileId' => $profileId->toString(), 'name' => 'test'],
+            json_decode($result2['event_payload'], true),
+        );
+
+        $result3 = $result[2];
+
+        self::assertEquals(43, $result3['id']);
+        self::assertEquals(sprintf('profile-%s', $profileId->toString()), $result3['stream']);
+        self::assertEquals('3', $result3['playhead']);
+        self::assertStringContainsString('2020-01-02 00:00:00', $result3['recorded_on']);
+        self::assertEquals('profile.created', $result3['event_name']);
+        self::assertEquals(
+            ['profileId' => $profileId->toString(), 'name' => 'test'],
+            json_decode($result3['event_payload'], true),
+        );
+    }
+
+    public function testSaveWithOnlyStreamName(): void
+    {
+        $messages = [
+            Message::create(new ExternEvent('test 1'))
+                ->withHeader(new StreamNameHeader('extern')),
+            Message::create(new ExternEvent('test 2'))
+                ->withHeader(new StreamNameHeader('extern')),
+        ];
+
+        $this->store->save(...$messages);
+
+        /** @var list<array<string, string>> $result */
+        $result = $this->connection->fetchAllAssociative('SELECT * FROM event_store');
+
+        self::assertCount(2, $result);
+
+        $result1 = $result[0];
+
+        self::assertEquals('extern', $result1['stream']);
+        self::assertEquals(null, $result1['playhead']);
+        self::assertStringContainsString('2020-01-01 00:00:00', $result1['recorded_on']);
+        self::assertEquals('extern', $result1['event_name']);
+        self::assertEquals(
+            ['message' => 'test 1'],
+            json_decode($result1['event_payload'], true),
+        );
+
+        $result2 = $result[1];
+
+        self::assertEquals('extern', $result2['stream']);
+        self::assertEquals(null, $result2['playhead']);
+        self::assertStringContainsString('2020-01-01 00:00:00', $result2['recorded_on']);
+        self::assertEquals('extern', $result2['event_name']);
+        self::assertEquals(
+            ['message' => 'test 2'],
+            json_decode($result2['event_payload'], true),
+        );
+    }
+
+    public function testSaveWithTransactional(): void
+    {
+        $profileId = ProfileId::generate();
+
+        $messages = [
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(1))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00'))),
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(2))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-02 00:00:00'))),
+        ];
+
+        $this->store->transactional(function () use ($messages): void {
+            $this->store->save(...$messages);
+        });
+
+        /** @var list<array<string, string>> $result */
+        $result = $this->connection->fetchAllAssociative('SELECT * FROM event_store');
+
+        self::assertCount(2, $result);
+
+        $result1 = $result[0];
+
+        self::assertEquals(sprintf('profile-%s', $profileId->toString()), $result1['stream']);
+        self::assertEquals('1', $result1['playhead']);
+        self::assertStringContainsString('2020-01-01 00:00:00', $result1['recorded_on']);
+        self::assertEquals('profile.created', $result1['event_name']);
+        self::assertEquals(
+            ['profileId' => $profileId->toString(), 'name' => 'test'],
+            json_decode($result1['event_payload'], true),
+        );
+
+        $result2 = $result[1];
+
+        self::assertEquals(sprintf('profile-%s', $profileId->toString()), $result2['stream']);
+        self::assertEquals('2', $result2['playhead']);
+        self::assertStringContainsString('2020-01-02 00:00:00', $result2['recorded_on']);
+        self::assertEquals('profile.created', $result2['event_name']);
+        self::assertEquals(
+            ['profileId' => $profileId->toString(), 'name' => 'test'],
+            json_decode($result2['event_payload'], true),
+        );
+    }
+
+    public function testArchive(): void
+    {
+        $profileId = ProfileId::generate();
+
+        $messages = [
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(1))
+                ->withHeader(new EventIdHeader('1'))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00'))),
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(2))
+                ->withHeader(new EventIdHeader('2'))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-02 00:00:00'))),
+        ];
+
+        $this->store->save(...$messages);
+        $this->store->archive(
+            new Criteria(
+                new StreamCriterion(sprintf('profile-%s', $profileId->toString())),
+                new ToPlayheadCriterion(2),
+            ),
+        );
+
+        /** @var list<array<string, string>> $result */
+        $result = $this->connection->fetchAllAssociative('SELECT * FROM event_store ORDER BY id');
+
+        self::assertCount(2, $result);
+
+        $result1 = $result[0];
+
+        self::assertEquals(sprintf('profile-%s', $profileId->toString()), $result1['stream']);
+        self::assertEquals('1', $result1['playhead']);
+        self::assertStringContainsString('2020-01-01 00:00:00', $result1['recorded_on']);
+        self::assertEquals('profile.created', $result1['event_name']);
+        self::assertEquals(
+            ['profileId' => $profileId->toString(), 'name' => 'test'],
+            json_decode($result1['event_payload'], true),
+        );
+
+        self::assertEquals('1', $result1['archived']);
+
+        $result2 = $result[1];
+
+        self::assertEquals(sprintf('profile-%s', $profileId->toString()), $result2['stream']);
+        self::assertEquals('2', $result2['playhead']);
+        self::assertStringContainsString('2020-01-02 00:00:00', $result2['recorded_on']);
+        self::assertEquals('profile.created', $result2['event_name']);
+        self::assertEquals(
+            ['profileId' => $profileId->toString(), 'name' => 'test'],
+            json_decode($result2['event_payload'], true),
+        );
+
+        self::assertEquals('0', $result2['archived']);
+    }
+
+    public function testUniqueStreamNameAndPlayheadConstraint(): void
+    {
+        $this->expectException(UniqueConstraintViolation::class);
+
+        $profileId = ProfileId::generate();
+
+        $messages = [
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(1))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00'))),
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(1))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00'))),
+        ];
+
+        $this->store->save(...$messages);
+    }
+
+    public function testUniqueEventIdConstraint(): void
+    {
+        $this->expectException(UniqueConstraintViolation::class);
+
+        $profileId = ProfileId::generate();
+
+        $messages = [
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new EventIdHeader('1'))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00'))),
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new EventIdHeader('1'))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00'))),
+        ];
+
+        $this->store->save(...$messages);
+    }
+
+    public function testSave10000Messages(): void
+    {
+        $profileId = ProfileId::generate();
+
+        $messages = [];
+
+        for ($i = 1; $i <= 10000; $i++) {
+            $messages[] = Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader($i))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')));
+        }
+
+        $this->store->save(...$messages);
+
+        /** @var int $result */
+        $result = $this->connection->fetchFirstColumn('SELECT COUNT(*) FROM event_store')[0];
+
+        self::assertEquals(10000, $result);
+    }
+
+    public function testLoad(): void
+    {
+        $profileId = ProfileId::generate();
+
+        $message = Message::create(new ProfileCreated($profileId, 'test'))
+            ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+            ->withHeader(new PlayheadHeader(1))
+            ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')));
+
+        $this->store->save($message);
+
+        $stream = null;
+
+        try {
+            $stream = $this->store->load();
+
+            self::assertSame(1, $stream->index());
+            self::assertSame(0, $stream->position());
+
+            $loadedMessage = $stream->current();
+
+            self::assertInstanceOf(Message::class, $loadedMessage);
+            self::assertNotSame($message, $loadedMessage);
+            self::assertEquals($message->event(), $loadedMessage->event());
+            self::assertEquals(
+                $message->header(StreamNameHeader::class)->streamName,
+                $loadedMessage->header(StreamNameHeader::class)->streamName,
+            );
+            self::assertEquals(
+                $message->header(PlayheadHeader::class)->playhead,
+                $loadedMessage->header(PlayheadHeader::class)->playhead,
+            );
+            self::assertEquals(
+                $message->header(RecordedOnHeader::class)->recordedOn,
+                $loadedMessage->header(RecordedOnHeader::class)->recordedOn,
+            );
+        } finally {
+            $stream?->close();
+        }
+    }
+
+    public function testLoadWithWildcard(): void
+    {
+        $profileId1 = ProfileId::generate();
+        $profileId2 = ProfileId::generate();
+
+        $messages = [
+            Message::create(new ProfileCreated($profileId1, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId1->toString())))
+                ->withHeader(new PlayheadHeader(1))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00'))),
+            Message::create(new ProfileCreated($profileId2, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId2->toString())))
+                ->withHeader(new PlayheadHeader(1))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00'))),
+            Message::create(new ExternEvent('test message'))
+                ->withHeader(new StreamNameHeader('foo')),
+        ];
+
+        $this->store->save(...$messages);
+
+        $stream = null;
+
+        try {
+            $stream = $this->store->load(new Criteria(new StreamCriterion('profile-*')));
+
+            $messages = iterator_to_array($stream);
+
+            self::assertCount(2, $messages);
+        } finally {
+            $stream?->close();
+        }
+
+        try {
+            $stream = $this->store->load(new Criteria(new StreamCriterion('*-*')));
+
+            $messages = iterator_to_array($stream);
+
+            self::assertCount(2, $messages);
+        } finally {
+            $stream?->close();
+        }
+    }
+
+    public function testTags(): void
+    {
+        $profileId1 = ProfileId::generate();
+        $profileId2 = ProfileId::generate();
+
+        $messages = [
+            Message::create(new ProfileCreated($profileId1, 'test'))
+                ->withHeader(new StreamNameHeader('foo'))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+                ->withHeader(new TagsHeader(['profile:' . $profileId1->toString()])),
+            Message::create(new ProfileCreated($profileId2, 'test'))
+                ->withHeader(new StreamNameHeader('foo'))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+                ->withHeader(new TagsHeader(['profile:' . $profileId2->toString()])),
+            Message::create(new ExternEvent('test message'))
+                ->withHeader(new StreamNameHeader('foo'))
+                ->withHeader(new TagsHeader([
+                    'profile:' . $profileId1->toString(),
+                    'profile:' . $profileId2->toString(),
+                ])),
+        ];
+
+        $this->store->save(...$messages);
+
+        $stream = null;
+
+        try {
+            $stream = $this->store->load(
+                new Criteria(
+                    new TagCriterion('profile:' . $profileId1->toString()),
+                ),
+            );
+
+            $messages = iterator_to_array($stream);
+
+            self::assertCount(2, $messages);
+
+            self::assertEquals(
+                ['profile:' . $profileId1->toString()],
+                $messages[0]->header(TagsHeader::class)->tags,
+            );
+
+            self::assertEquals(
+                ['profile:' . $profileId1->toString(), 'profile:' . $profileId2->toString()],
+                $messages[1]->header(TagsHeader::class)->tags,
+            );
+        } finally {
+            $stream?->close();
+        }
+    }
+
+    public function testStreams(): void
+    {
+        $profileId = ProfileId::fromString('0190e47e-77e9-7b90-bf62-08bbf0ab9b4b');
+
+        $messages = [
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(1))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00'))),
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(2))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00'))),
+            Message::create(new ExternEvent('test message'))
+                ->withHeader(new StreamNameHeader('foo')),
+        ];
+
+        $this->store->save(...$messages);
+
+        $streams = $this->store->streams();
+
+        self::assertEquals([
+            'foo',
+            'profile-0190e47e-77e9-7b90-bf62-08bbf0ab9b4b',
+        ], $streams);
+    }
+
+    public function testRemove(): void
+    {
+        $profileId = ProfileId::fromString('0190e47e-77e9-7b90-bf62-08bbf0ab9b4b');
+
+        $messages = [
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(1))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00'))),
+            Message::create(new ProfileCreated($profileId, 'test'))
+                ->withHeader(new StreamNameHeader(sprintf('profile-%s', $profileId->toString())))
+                ->withHeader(new PlayheadHeader(2))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00'))),
+            Message::create(new ExternEvent('test message'))
+                ->withHeader(new StreamNameHeader('foo')),
+        ];
+
+        $this->store->save(...$messages);
+
+        $streams = $this->store->streams();
+
+        self::assertEquals([
+            'foo',
+            'profile-0190e47e-77e9-7b90-bf62-08bbf0ab9b4b',
+        ], $streams);
+
+        $this->store->remove(new Criteria(new StreamCriterion('profile-*')));
+
+        $streams = $this->store->streams();
+
+        self::assertEquals(['foo'], $streams);
+    }
+}

From 919bdbbbfcf2d6f4b186291b2b0fccf293c4b263 Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Mon, 28 Jul 2025 12:53:54 +0200
Subject: [PATCH 02/22] dcb poc

---
 docs/pages/dynamic_consistency_boundary.md    |   2 +
 src/Attribute/EventTag.php                    |  16 ++
 src/DCB/AppendCondition.php                   |  16 ++
 src/DCB/AttributeEventTagExtractor.php        |  58 ++++
 src/DCB/CompositeProjection.php               |  95 +++++++
 src/DCB/DecisionModel.php                     |  50 ++++
 src/DCB/DecisionModelBuilder.php              |  14 +
 src/DCB/EventAppender.php                     |  12 +
 src/DCB/EventTagExtractor.php                 |  12 +
 src/DCB/HighestSequenceNumber.php             |  24 ++
 src/DCB/Projection.php                        |  41 +++
 src/DCB/StoreDecisionModelBuilder.php         |  50 ++++
 src/DCB/StoreEventAppender.php                |  35 +++
 .../MessageDecorator/EventTagDecorator.php    |  25 ++
 src/Store/Criteria/TagCriterion.php           |  15 +-
 src/Store/Header/TagsHeader.php               |   7 +-
 src/Store/TaggableDoctrineDbalStore.php       | 249 +++++++++++++++---
 .../Course/Command/ChangeCourseCapacity.php   |  16 ++
 .../Course/Command/DefineCourse.php           |  16 ++
 .../Command/SubscribeStudentToCourse.php      |  17 ++
 .../Course/CourseId.php                       |  13 +
 .../Course/Event/CourseCapacityChanged.php    |  20 ++
 .../Course/Event/CourseDefined.php            |  20 ++
 .../Event/StudentSubscribedToCourse.php       |  22 ++
 .../Handler/ChangeCourseCapacityHandler.php   |  49 ++++
 .../Course/Handler/DefineCourseHandler.php    |  43 +++
 .../SubscribeStudentToCourseHandler.php       |  66 +++++
 .../Projection/CourseCapacityProjection.php   |  42 +++
 .../Course/Projection/CourseExists.php        |  36 +++
 .../NumberOfCourseSubscriptionsProjection.php |  35 +++
 ...NumberOfStudentSubscriptionsProjection.php |  35 +++
 .../StudentAlreadySubscribedProjection.php    |  40 +++
 .../Course/StudentId.php                      |  13 +
 .../DynamicConsistencyBoundaryTest.php        | 115 ++++++++
 .../Invoice/Command/CreateInvoice.php         |  13 +
 .../Invoice/Event/InvoiceCreated.php          |  19 ++
 .../Invoice/Handler/CreateInvoiceHandler.php  |  38 +++
 .../NextInvoiceNumberProjection.php           |  27 ++
 .../Store/TaggableDoctrineDbalStoreTest.php   | 108 +++++++-
 39 files changed, 1470 insertions(+), 54 deletions(-)
 create mode 100644 docs/pages/dynamic_consistency_boundary.md
 create mode 100644 src/Attribute/EventTag.php
 create mode 100644 src/DCB/AppendCondition.php
 create mode 100644 src/DCB/AttributeEventTagExtractor.php
 create mode 100644 src/DCB/CompositeProjection.php
 create mode 100644 src/DCB/DecisionModel.php
 create mode 100644 src/DCB/DecisionModelBuilder.php
 create mode 100644 src/DCB/EventAppender.php
 create mode 100644 src/DCB/EventTagExtractor.php
 create mode 100644 src/DCB/HighestSequenceNumber.php
 create mode 100644 src/DCB/Projection.php
 create mode 100644 src/DCB/StoreDecisionModelBuilder.php
 create mode 100644 src/DCB/StoreEventAppender.php
 create mode 100644 src/Repository/MessageDecorator/EventTagDecorator.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/Command/ChangeCourseCapacity.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/Command/DefineCourse.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/Command/SubscribeStudentToCourse.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/CourseId.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/Event/CourseCapacityChanged.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/Event/CourseDefined.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/Event/StudentSubscribedToCourse.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/Handler/ChangeCourseCapacityHandler.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/Handler/DefineCourseHandler.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/Handler/SubscribeStudentToCourseHandler.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Course/StudentId.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Invoice/Command/CreateInvoice.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Invoice/Event/InvoiceCreated.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Invoice/Handler/CreateInvoiceHandler.php
 create mode 100644 tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php

diff --git a/docs/pages/dynamic_consistency_boundary.md b/docs/pages/dynamic_consistency_boundary.md
new file mode 100644
index 00000000..7064df33
--- /dev/null
+++ b/docs/pages/dynamic_consistency_boundary.md
@@ -0,0 +1,2 @@
+# Dynamic Consistency Boundary
+
diff --git a/src/Attribute/EventTag.php b/src/Attribute/EventTag.php
new file mode 100644
index 00000000..e2506fcc
--- /dev/null
+++ b/src/Attribute/EventTag.php
@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Attribute;
+
+use Attribute;
+
+#[Attribute(Attribute::TARGET_PROPERTY)]
+final class EventTag
+{
+    public function __construct(
+        public readonly string|null $prefix = null,
+    ) {
+    }
+}
diff --git a/src/DCB/AppendCondition.php b/src/DCB/AppendCondition.php
new file mode 100644
index 00000000..51f7cbfe
--- /dev/null
+++ b/src/DCB/AppendCondition.php
@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+/** @experimental */
+final class AppendCondition
+{
+    /** @param list<list<string>> $tags */
+    public function __construct(
+        public readonly array $tags,
+        public readonly HighestSequenceNumber|null $expectedHighestSequenceNumber = null,
+    ) {
+    }
+}
diff --git a/src/DCB/AttributeEventTagExtractor.php b/src/DCB/AttributeEventTagExtractor.php
new file mode 100644
index 00000000..49618d4a
--- /dev/null
+++ b/src/DCB/AttributeEventTagExtractor.php
@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+use Patchlevel\EventSourcing\Aggregate\AggregateRootId;
+use Patchlevel\EventSourcing\Attribute\EventTag;
+use ReflectionClass;
+use RuntimeException;
+
+use function array_keys;
+use function get_debug_type;
+use function is_int;
+use function is_string;
+use function sprintf;
+
+/** @experimental */
+final class AttributeEventTagExtractor implements EventTagExtractor
+{
+    /** @return list<string> */
+    public function extract(object $event): array
+    {
+        $reflectionClass = new ReflectionClass($event);
+
+        $tags = [];
+
+        foreach ($reflectionClass->getProperties() as $property) {
+            $attributes = $property->getAttributes(EventTag::class);
+
+            if ($attributes === []) {
+                continue;
+            }
+
+            $attribute = $attributes[0]->newInstance();
+
+            $value = $property->getValue($event);
+
+            if ($value instanceof AggregateRootId) {
+                $value = $value->toString();
+            }
+
+            if (!is_string($value) && !is_int($value)) {
+                throw new RuntimeException(
+                    sprintf('Event tag value must be a string or an int, %s given', get_debug_type($value)),
+                );
+            }
+
+            if ($attribute->prefix) {
+                $value = $attribute->prefix . ':' . $value;
+            }
+
+            $tags[(string)$value] = true;
+        }
+
+        return array_keys($tags);
+    }
+}
diff --git a/src/DCB/CompositeProjection.php b/src/DCB/CompositeProjection.php
new file mode 100644
index 00000000..628c9726
--- /dev/null
+++ b/src/DCB/CompositeProjection.php
@@ -0,0 +1,95 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Store\Header\TagsHeader;
+
+use function array_diff;
+use function array_map;
+use function array_merge;
+use function array_unique;
+use function array_values;
+use function in_array;
+use function sort;
+
+/**
+ * @experimental
+ * @extends Projection<array<string, mixed>>
+ */
+final class CompositeProjection extends Projection
+{
+    /** @param array<string, Projection> $projections */
+    public function __construct(
+        private readonly array $projections,
+    ) {
+    }
+
+    /** @return list<string> */
+    public function tagFilter(): array
+    {
+        $tags = [];
+
+        foreach ($this->projections as $projection) {
+            $tags = array_merge($tags, $projection->tagFilter());
+        }
+
+        return array_values(array_unique($tags));
+    }
+
+    /** @return list<list<string>> */
+    public function groupedTagFilter(): array
+    {
+        $result = [];
+
+        foreach ($this->projections as $projection) {
+            $tags = $projection->tagFilter();
+
+            sort($tags);
+
+            if (in_array($tags, $result, true)) {
+                continue;
+            }
+
+            $result[] = $tags;
+        }
+
+        return $result;
+    }
+
+    /** @return array<string, mixed> */
+    public function initialState(): array
+    {
+        return array_map(static function (Projection $projection) {
+            return $projection->initialState();
+        }, $this->projections);
+    }
+
+    public function apply(mixed $state, Message $message): mixed
+    {
+        $tags = $message->header(TagsHeader::class)->tags;
+
+        foreach ($this->projections as $name => $projection) {
+            $neededTags = $projection->tagFilter();
+
+            if (!$this->isSubset($neededTags, $tags)) {
+                continue;
+            }
+
+            $state[$name] = $projection->apply($state[$name], $message);
+        }
+
+        return $state;
+    }
+
+    /**
+     * @param list<string> $needle
+     * @param list<string> $haystack
+     */
+    private function isSubset(array $needle, array $haystack): bool
+    {
+        return empty(array_diff($needle, $haystack));
+    }
+}
diff --git a/src/DCB/DecisionModel.php b/src/DCB/DecisionModel.php
new file mode 100644
index 00000000..5de31669
--- /dev/null
+++ b/src/DCB/DecisionModel.php
@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+use ArrayAccess;
+use LogicException;
+use OutOfBoundsException;
+
+use function array_key_exists;
+
+/**
+ * @experimental
+ * @psalm-immutable
+ * @implements ArrayAccess<string, mixed>
+ */
+final class DecisionModel implements ArrayAccess
+{
+    /** @param array<string, mixed> $state */
+    public function __construct(
+        public readonly array $state,
+        public readonly AppendCondition $appendCondition,
+    ) {
+    }
+
+    public function offsetExists(mixed $offset): bool
+    {
+        return array_key_exists($offset, $this->state);
+    }
+
+    public function offsetGet(mixed $offset): mixed
+    {
+        if (!$this->offsetExists($offset)) {
+            throw new OutOfBoundsException("Offset '$offset' does not exist in the state.");
+        }
+
+        return $this->state[$offset];
+    }
+
+    public function offsetSet(mixed $offset, mixed $value): void
+    {
+        throw new LogicException('State is immutable, cannot set value.');
+    }
+
+    public function offsetUnset(mixed $offset): void
+    {
+        throw new LogicException('State is immutable, cannot unset value.');
+    }
+}
diff --git a/src/DCB/DecisionModelBuilder.php b/src/DCB/DecisionModelBuilder.php
new file mode 100644
index 00000000..90e64019
--- /dev/null
+++ b/src/DCB/DecisionModelBuilder.php
@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+/** @experimental */
+interface DecisionModelBuilder
+{
+    /** @param array<string, Projection> $projections */
+    public function build(
+        array $projections,
+    ): DecisionModel;
+}
diff --git a/src/DCB/EventAppender.php b/src/DCB/EventAppender.php
new file mode 100644
index 00000000..3e3c19ec
--- /dev/null
+++ b/src/DCB/EventAppender.php
@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+/** @experimental */
+interface EventAppender
+{
+    /** @param iterable<object> $events */
+    public function append(iterable $events, AppendCondition|null $appendCondition = null): void;
+}
diff --git a/src/DCB/EventTagExtractor.php b/src/DCB/EventTagExtractor.php
new file mode 100644
index 00000000..14906131
--- /dev/null
+++ b/src/DCB/EventTagExtractor.php
@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+/** @experimental */
+interface EventTagExtractor
+{
+    /** @return list<string> */
+    public function extract(object $event): array;
+}
diff --git a/src/DCB/HighestSequenceNumber.php b/src/DCB/HighestSequenceNumber.php
new file mode 100644
index 00000000..9d863f65
--- /dev/null
+++ b/src/DCB/HighestSequenceNumber.php
@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+/** @experimental */
+final class HighestSequenceNumber
+{
+    public function __construct(
+        public readonly int $value,
+    ) {
+    }
+
+    public static function none(): self
+    {
+        return new self(0);
+    }
+
+    public function isNone(): bool
+    {
+        return $this->value === 0;
+    }
+}
diff --git a/src/DCB/Projection.php b/src/DCB/Projection.php
new file mode 100644
index 00000000..6ab922da
--- /dev/null
+++ b/src/DCB/Projection.php
@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+use Patchlevel\EventSourcing\Message\Message;
+use ReflectionClass;
+
+use function method_exists;
+
+/**
+ * @experimental
+ * @template S as mixed
+ */
+abstract class Projection
+{
+    /** @return list<string> */
+    abstract public function tagFilter(): array;
+
+    /** @return S */
+    abstract public function initialState(): mixed;
+
+    /**
+     * @param S $state
+     *
+     * @return S
+     */
+    public function apply(mixed $state, Message $message): mixed
+    {
+        $event = $message->event();
+
+        $method = 'apply' . (new ReflectionClass($event))->getShortName();
+
+        if (method_exists($this, $method)) {
+            $state = $this->{$method}($state, $event);
+        }
+
+        return $state;
+    }
+}
diff --git a/src/DCB/StoreDecisionModelBuilder.php b/src/DCB/StoreDecisionModelBuilder.php
new file mode 100644
index 00000000..f7d2b0b5
--- /dev/null
+++ b/src/DCB/StoreDecisionModelBuilder.php
@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+use Patchlevel\EventSourcing\Store\Criteria\Criteria;
+use Patchlevel\EventSourcing\Store\Criteria\StreamCriterion;
+use Patchlevel\EventSourcing\Store\Criteria\TagCriterion;
+use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
+
+/** @experimental */
+final class StoreDecisionModelBuilder implements DecisionModelBuilder
+{
+    public function __construct(
+        private TaggableDoctrineDbalStore $store,
+    ) {
+    }
+
+    /** @param array<string, Projection> $projections */
+    public function build(
+        array $projections,
+    ): DecisionModel {
+        $projection = new CompositeProjection($projections);
+
+        $stream = $this->store->load(
+            new Criteria(
+                new StreamCriterion('main'),
+                new TagCriterion(...$projection->groupedTagFilter()),
+            ),
+        );
+
+        $state = $projection->initialState();
+
+        $highestId = 0;
+
+        foreach ($stream as $message) {
+            $highestId = $stream->index();
+            $state = $projection->apply($state, $message);
+        }
+
+        return new DecisionModel(
+            $state,
+            new AppendCondition(
+                $projection->groupedTagFilter(),
+                new HighestSequenceNumber($highestId ?? 0),
+            ),
+        );
+    }
+}
diff --git a/src/DCB/StoreEventAppender.php b/src/DCB/StoreEventAppender.php
new file mode 100644
index 00000000..c36f516e
--- /dev/null
+++ b/src/DCB/StoreEventAppender.php
@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
+use Patchlevel\EventSourcing\Store\Header\TagsHeader;
+use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
+
+use function array_map;
+
+/** @experimental */
+final class StoreEventAppender implements EventAppender
+{
+    public function __construct(
+        private readonly TaggableDoctrineDbalStore $store,
+        private readonly EventTagExtractor $eventTagExtractor = new AttributeEventTagExtractor(),
+    ) {
+    }
+
+    /** @param iterable<object> $events */
+    public function append(iterable $events, AppendCondition|null $appendCondition = null): void
+    {
+        $messages = array_map(
+            fn (object $event) => Message::create($event)
+                ->withHeader(new StreamNameHeader('main'))
+                ->withHeader(new TagsHeader($this->eventTagExtractor->extract($event))),
+            $events,
+        );
+
+        $this->store->append($messages, $appendCondition);
+    }
+}
diff --git a/src/Repository/MessageDecorator/EventTagDecorator.php b/src/Repository/MessageDecorator/EventTagDecorator.php
new file mode 100644
index 00000000..9b97b565
--- /dev/null
+++ b/src/Repository/MessageDecorator/EventTagDecorator.php
@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Repository\MessageDecorator;
+
+use Patchlevel\EventSourcing\DCB\AttributeEventTagExtractor;
+use Patchlevel\EventSourcing\DCB\EventTagExtractor;
+use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Store\Header\TagsHeader;
+
+final class EventTagDecorator implements MessageDecorator
+{
+    public function __construct(
+        private readonly EventTagExtractor $eventTagExtractor = new AttributeEventTagExtractor(),
+    ) {
+    }
+
+    public function __invoke(Message $message): Message
+    {
+        $tags = $this->eventTagExtractor->extract($message->event());
+
+        return $message->withHeader(new TagsHeader($tags));
+    }
+}
diff --git a/src/Store/Criteria/TagCriterion.php b/src/Store/Criteria/TagCriterion.php
index 957a3f9c..b4f3692c 100644
--- a/src/Store/Criteria/TagCriterion.php
+++ b/src/Store/Criteria/TagCriterion.php
@@ -4,23 +4,18 @@
 
 namespace Patchlevel\EventSourcing\Store\Criteria;
 
-use InvalidArgumentException;
-
-use function array_unique;
 use function array_values;
 
+/** @experimental */
 final class TagCriterion
 {
-    /** @var list<string> */
+    /** @var list<list<string>> */
     public readonly array $tags;
 
+    /** @param list<string> ...$tags */
     public function __construct(
-        string ...$tags,
+        array ...$tags,
     ) {
-        $this->tags = array_values(array_unique($tags));
-
-        if ($this->tags === []) {
-            throw new InvalidArgumentException('At least one tag must be provided.');
-        }
+        $this->tags = array_values($tags);
     }
 }
diff --git a/src/Store/Header/TagsHeader.php b/src/Store/Header/TagsHeader.php
index f52a6921..9cd3b2a8 100644
--- a/src/Store/Header/TagsHeader.php
+++ b/src/Store/Header/TagsHeader.php
@@ -4,8 +4,11 @@
 
 namespace Patchlevel\EventSourcing\Store\Header;
 
-/** @psalm-immutable */
-class TagsHeader
+/**
+ * @experimental
+ * @psalm-immutable
+ */
+final class TagsHeader
 {
     /** @param list<string> $tags */
     public function __construct(
diff --git a/src/Store/TaggableDoctrineDbalStore.php b/src/Store/TaggableDoctrineDbalStore.php
index 3605f4e6..a22125dd 100644
--- a/src/Store/TaggableDoctrineDbalStore.php
+++ b/src/Store/TaggableDoctrineDbalStore.php
@@ -13,10 +13,13 @@
 use Doctrine\DBAL\Platforms\PostgreSQLPlatform;
 use Doctrine\DBAL\Platforms\SQLitePlatform;
 use Doctrine\DBAL\Query\QueryBuilder;
+use Doctrine\DBAL\Schema\Name\UnqualifiedName;
+use Doctrine\DBAL\Schema\PrimaryKeyConstraint;
 use Doctrine\DBAL\Schema\Schema;
 use Doctrine\DBAL\Types\Type;
 use Doctrine\DBAL\Types\Types;
 use Patchlevel\EventSourcing\Clock\SystemClock;
+use Patchlevel\EventSourcing\DCB\AppendCondition;
 use Patchlevel\EventSourcing\Message\HeaderNotFound;
 use Patchlevel\EventSourcing\Message\Message;
 use Patchlevel\EventSourcing\Message\Serializer\DefaultHeadersSerializer;
@@ -42,9 +45,11 @@
 use PDO;
 use Psr\Clock\ClockInterface;
 use Ramsey\Uuid\Uuid;
+use RuntimeException;
 
 use function array_fill;
 use function array_filter;
+use function array_map;
 use function array_merge;
 use function array_values;
 use function class_exists;
@@ -55,6 +60,7 @@
 use function in_array;
 use function is_int;
 use function is_string;
+use function json_encode;
 use function sprintf;
 use function str_contains;
 use function str_replace;
@@ -124,7 +130,7 @@ public function load(
     ): TaggableDoctrineDbalStoreStream {
         $builder = $this->connection->createQueryBuilder()
             ->select('*')
-            ->from($this->config['table_name'])
+            ->from($this->config['table_name'], 'events')
             ->orderBy('id', $backwards ? 'DESC' : 'ASC');
 
         $this->applyCriteria($builder, $criteria ?? new Criteria());
@@ -224,17 +230,7 @@ private function applyCriteria(QueryBuilder $builder, Criteria $criteria): void
                     $builder->setParameter('event_id', $criterion->eventId, ArrayParameterType::STRING);
                     break;
                 case TagCriterion::class:
-                    if ($this->isSQLite) {
-                        $builder->andWhere('NOT EXISTS(SELECT value FROM JSON_EACH(:tags) WHERE value NOT IN (SELECT value FROM JSON_EACH(tags)))');
-                    } elseif ($this->isPostgres) {
-                        $builder->andWhere('tags @> :tags::jsonb');
-                    } elseif ($this->isMysql || $this->isMariaDb) {
-                        $builder->andWhere('JSON_CONTAINS(tags, :tags)');
-                    } else {
-                        throw new UnsupportedCriterion($criterion::class);
-                    }
-
-                    $builder->setParameter('tags', $criterion->tags, Types::JSON);
+                    $this->queryCondition($builder, $criterion->tags);
                     break;
                 default:
                     throw new UnsupportedCriterion($criterion::class);
@@ -286,42 +282,31 @@ function () use ($messages): void {
 
                     $data = $this->eventSerializer->serialize($message->event());
 
-                    try {
-                        $streamName = $message->header(StreamNameHeader::class)->streamName;
-                        $parameters[] = $streamName;
-                    } catch (HeaderNotFound $e) {
-                        throw new MissingDataForStorage($e->name, $e);
-                    }
+                    $parameters[] = $message->hasHeader(StreamNameHeader::class)
+                        ? $message->header(StreamNameHeader::class)->streamName
+                        : 'default';
 
-                    if ($message->hasHeader(PlayheadHeader::class)) {
-                        $parameters[] = $message->header(PlayheadHeader::class)->playhead;
-                    } else {
-                        $parameters[] = null;
-                    }
+                    $parameters[] = $message->hasHeader(PlayheadHeader::class)
+                        ? $message->header(PlayheadHeader::class)->playhead
+                        : null;
 
-                    if ($message->hasHeader(EventIdHeader::class)) {
-                        $eventId = $message->header(EventIdHeader::class)->eventId;
-                    } else {
-                        $eventId = Uuid::uuid7()->toString();
-                    }
+                    $eventId = $message->hasHeader(EventIdHeader::class)
+                        ? $message->header(EventIdHeader::class)->eventId
+                        : Uuid::uuid7()->toString();
 
                     $parameters[] = $eventId;
                     $parameters[] = $data->name;
                     $parameters[] = $data->payload;
 
-                    if ($message->hasHeader(TagsHeader::class)) {
-                        $parameters[] = $message->header(TagsHeader::class)->tags;
-                    } else {
-                        $parameters[] = [];
-                    }
+                    $parameters[] = $message->hasHeader(TagsHeader::class)
+                        ? $message->header(TagsHeader::class)->tags
+                        : [];
 
                     $types[$offset + 5] = $jsonType;
 
-                    if ($message->hasHeader(RecordedOnHeader::class)) {
-                        $parameters[] = $message->header(RecordedOnHeader::class)->recordedOn;
-                    } else {
-                        $parameters[] = $this->clock->now();
-                    }
+                    $parameters[] = $message->hasHeader(RecordedOnHeader::class)
+                        ? $message->header(RecordedOnHeader::class)->recordedOn
+                        : $this->clock->now();
 
                     $types[$offset + 6] = $dateTimeType;
 
@@ -374,6 +359,135 @@ function () use ($messages): void {
         );
     }
 
+    /** @param iterable<Message> $messages */
+    public function append(iterable $messages, AppendCondition|null $appendCondition = null): void
+    {
+        $this->transactional(function () use ($messages, $appendCondition): void {
+            $booleanType = Type::getType(Types::BOOLEAN);
+            $dateTimeType = Type::getType(Types::DATETIMETZ_IMMUTABLE);
+            $jsonType = Type::getType(Types::JSON);
+
+            $columns = [
+                'stream',
+                'playhead',
+                'event_id',
+                'event_name',
+                'event_payload',
+                'tags',
+                'recorded_on',
+                'archived',
+                'custom_headers',
+            ];
+
+            $selects = [];
+            $parameters = [];
+            $types = [];
+
+            $columnsLength = count($columns);
+            //$batchSize = (int)floor(self::MAX_UNSIGNED_SMALL_INT / $columnsLength);
+            $position = 0;
+
+            foreach ($messages as $message) {
+                $selects[] = sprintf('SELECT %s', implode(', ', array_map(
+                    static fn (string $column) => ':' . $column . $position,
+                    $columns,
+                )));
+
+                /** @var int<0, max> $offset */
+                $offset = $position * $columnsLength;
+
+                $data = $this->eventSerializer->serialize($message->event());
+
+                $parameters['stream' . $position] = $message->hasHeader(StreamNameHeader::class)
+                    ? $message->header(StreamNameHeader::class)->streamName
+                    : 'default';
+
+                $parameters['playhead' . $position] = $message->hasHeader(PlayheadHeader::class)
+                    ? $message->header(PlayheadHeader::class)->playhead
+                    : null;
+
+                $eventId = $message->hasHeader(EventIdHeader::class)
+                    ? $message->header(EventIdHeader::class)->eventId
+                    : Uuid::uuid7()->toString();
+
+                $parameters['event_id' . $position] = $eventId;
+                $parameters['event_name' . $position] = $data->name;
+                $parameters['event_payload' . $position] = $data->payload;
+
+                $parameters['tags' . $position] = $message->hasHeader(TagsHeader::class)
+                    ? $message->header(TagsHeader::class)->tags
+                    : [];
+
+                $types['tags' . $position] = $jsonType;
+
+                $parameters['recorded_on' . $position] = $message->hasHeader(RecordedOnHeader::class)
+                    ? $message->header(RecordedOnHeader::class)->recordedOn
+                    : $this->clock->now();
+
+                $types['recorded_on' . $position] = $dateTimeType;
+
+                $parameters['archived' . $position] = $message->hasHeader(ArchivedHeader::class);
+                $types['archived' . $position] = $booleanType;
+
+                $parameters['custom_headers' . $position] = $this->headersSerializer->serialize($this->getCustomHeaders($message));
+
+                $position++;
+
+                /*
+                if ($position !== $batchSize) {
+                    continue;
+                }
+
+                $this->executeSave($columns, $placeholders, $parameters, $types, $this->connection);
+                */
+            }
+
+            $query = sprintf(
+                'INSERT INTO %s (%s) %s',
+                $this->config['table_name'],
+                implode(', ', $columns),
+                implode(' UNION ALL ', $selects),
+            );
+
+            if ($appendCondition instanceof AppendCondition && $appendCondition->tags !== []) {
+                $queryBuilder = $this->connection->createQueryBuilder()
+                    ->select('events.id')
+                    ->from($this->config['table_name'], 'events')
+                    ->orderBy('events.id', 'DESC')
+                    ->setMaxResults(1);
+
+                $this->queryCondition($queryBuilder, $appendCondition->tags);
+
+                if ($appendCondition->expectedHighestSequenceNumber->isNone()) {
+                    $query .= ' WHERE NOT EXISTS (' . $queryBuilder->getSQL() . ')';
+                } else {
+                    $query .= ' WHERE (' . $queryBuilder->getSQL() . ') = :highestId';
+                    $parameters['highestId'] = $appendCondition->expectedHighestSequenceNumber->value;
+                }
+
+                $parameters = array_merge(
+                    $parameters,
+                    $queryBuilder->getParameters(),
+                );
+
+                $types = array_merge(
+                    $types,
+                    $queryBuilder->getParameterTypes(),
+                );
+            }
+
+            try {
+                $affectedRows = $this->connection->executeStatement($query, $parameters, $types);
+
+                if ($affectedRows === 0 && $appendCondition->expectedHighestSequenceNumber !== null) {
+                    throw new UniqueConstraintViolation();
+                }
+            } catch (UniqueConstraintViolationException $e) {
+                throw new UniqueConstraintViolation($e);
+            }
+        });
+    }
+
     /**
      * @param Closure():ClosureReturn $function
      *
@@ -471,7 +585,11 @@ public function configureSchema(Schema $schema, Connection $connection): void
         $table->addColumn('custom_headers', Types::JSON)
             ->setNotnull(true);
 
-        $table->setPrimaryKey(['id']);
+        $table->addPrimaryKeyConstraint(
+            PrimaryKeyConstraint::editor()->setColumnNames(
+                UnqualifiedName::unquoted('id'),
+            )->create(),
+        );
         $table->addUniqueIndex(['event_id']);
         $table->addUniqueIndex(['stream', 'playhead']);
         $table->addIndex(['stream', 'playhead', 'archived']);
@@ -487,6 +605,7 @@ private function getCustomHeaders(Message $message): array
             PlayheadHeader::class,
             RecordedOnHeader::class,
             ArchivedHeader::class,
+            TagsHeader::class,
         ];
 
         return array_values(
@@ -654,4 +773,56 @@ private function unlock(): void
             $this->connection->getDatabasePlatform()::class,
         );
     }
+
+    /** @return Closure(): string */
+    private function uniqueParameterGenerator(): Closure
+    {
+        return static function () {
+            static $counter = 0;
+
+            return 'param' . ++$counter;
+        };
+    }
+
+    /** @param list<list<string>> $tagGroups */
+    private function queryCondition(QueryBuilder $builder, array $tagGroups): void
+    {
+        $subqueries = [];
+
+        $uniqueParameterGenerator = $this->uniqueParameterGenerator();
+
+        foreach ($tagGroups as $tags) {
+            $subQueryBuilder = $this->connection->createQueryBuilder()
+                ->select('id')
+                ->from($this->config['table_name']);
+
+            $parameterName = $uniqueParameterGenerator();
+
+            if ($this->isSQLite) {
+                $subQueryBuilder->andWhere("NOT EXISTS(SELECT value FROM JSON_EACH(:{$parameterName}) WHERE value NOT IN (SELECT value FROM JSON_EACH(tags)))");
+            } elseif ($this->isPostgres) {
+                $subQueryBuilder->andWhere("tags @> :{$parameterName}::jsonb");
+            } elseif ($this->isMysql || $this->isMariaDb) {
+                $subQueryBuilder->andWhere("JSON_CONTAINS(tags, :{$parameterName})");
+            } else {
+                throw new RuntimeException('x');
+            }
+
+            $builder->setParameter($parameterName, json_encode($tags));
+
+            $subqueries[] = $subQueryBuilder->getSQL();
+        }
+
+        $joinQueryBuilder = $this->connection->createQueryBuilder()
+            ->select('id')
+            ->from('(' . implode(' UNION ALL ', $subqueries) . ')', 'j')
+            ->groupBy('j.id');
+
+        $builder->innerJoin(
+            'events',
+            '(' . $joinQueryBuilder->getSQL() . ')',
+            'ej',
+            'ej.id = events.id',
+        );
+    }
 }
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Command/ChangeCourseCapacity.php b/tests/Integration/DynamicConsistencyBoundary/Course/Command/ChangeCourseCapacity.php
new file mode 100644
index 00000000..fea9991a
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Command/ChangeCourseCapacity.php
@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Command;
+
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
+
+final class ChangeCourseCapacity
+{
+    public function __construct(
+        public readonly CourseId $courseId,
+        public readonly int $capacity,
+    ) {
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Command/DefineCourse.php b/tests/Integration/DynamicConsistencyBoundary/Course/Command/DefineCourse.php
new file mode 100644
index 00000000..88428ff0
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Command/DefineCourse.php
@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Command;
+
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
+
+final class DefineCourse
+{
+    public function __construct(
+        public readonly CourseId $courseId,
+        public readonly int $capacity,
+    ) {
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Command/SubscribeStudentToCourse.php b/tests/Integration/DynamicConsistencyBoundary/Course/Command/SubscribeStudentToCourse.php
new file mode 100644
index 00000000..5bf5e5bf
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Command/SubscribeStudentToCourse.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Command;
+
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\StudentId;
+
+final class SubscribeStudentToCourse
+{
+    public function __construct(
+        public readonly StudentId $studentId,
+        public readonly CourseId $courseId,
+    ) {
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/CourseId.php b/tests/Integration/DynamicConsistencyBoundary/Course/CourseId.php
new file mode 100644
index 00000000..26cedff3
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/CourseId.php
@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course;
+
+use Patchlevel\EventSourcing\Aggregate\AggregateRootId;
+use Patchlevel\EventSourcing\Aggregate\RamseyUuidV7Behaviour;
+
+final class CourseId implements AggregateRootId
+{
+    use RamseyUuidV7Behaviour;
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Event/CourseCapacityChanged.php b/tests/Integration/DynamicConsistencyBoundary/Course/Event/CourseCapacityChanged.php
new file mode 100644
index 00000000..40c757dd
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Event/CourseCapacityChanged.php
@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event;
+
+use Patchlevel\EventSourcing\Attribute\Event;
+use Patchlevel\EventSourcing\Attribute\EventTag;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
+
+#[Event('course.capacity_changed')]
+final class CourseCapacityChanged
+{
+    public function __construct(
+        #[EventTag(prefix: 'course')]
+        public CourseId $courseId,
+        public int $capacity,
+    ) {
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Event/CourseDefined.php b/tests/Integration/DynamicConsistencyBoundary/Course/Event/CourseDefined.php
new file mode 100644
index 00000000..cf4f24b3
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Event/CourseDefined.php
@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event;
+
+use Patchlevel\EventSourcing\Attribute\Event;
+use Patchlevel\EventSourcing\Attribute\EventTag;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
+
+#[Event('course.defined')]
+final class CourseDefined
+{
+    public function __construct(
+        #[EventTag(prefix: 'course')]
+        public CourseId $courseId,
+        public int $capacity,
+    ) {
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Event/StudentSubscribedToCourse.php b/tests/Integration/DynamicConsistencyBoundary/Course/Event/StudentSubscribedToCourse.php
new file mode 100644
index 00000000..fae30c25
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Event/StudentSubscribedToCourse.php
@@ -0,0 +1,22 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event;
+
+use Patchlevel\EventSourcing\Attribute\Event;
+use Patchlevel\EventSourcing\Attribute\EventTag;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\StudentId;
+
+#[Event('course.student_subscribed')]
+final class StudentSubscribedToCourse
+{
+    public function __construct(
+        #[EventTag(prefix: 'student')]
+        public readonly StudentId $studentId,
+        #[EventTag(prefix: 'course')]
+        public readonly CourseId $courseId,
+    ) {
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Handler/ChangeCourseCapacityHandler.php b/tests/Integration/DynamicConsistencyBoundary/Course/Handler/ChangeCourseCapacityHandler.php
new file mode 100644
index 00000000..35f7aa6b
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Handler/ChangeCourseCapacityHandler.php
@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Handler;
+
+use Patchlevel\EventSourcing\Attribute\Handle;
+use Patchlevel\EventSourcing\DCB\DecisionModelBuilder;
+use Patchlevel\EventSourcing\DCB\EventAppender;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Command\ChangeCourseCapacity;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseCapacityChanged;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection\CourseCapacityProjection;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection\CourseExists;
+use RuntimeException;
+
+final class ChangeCourseCapacityHandler
+{
+    public function __construct(
+        private readonly DecisionModelBuilder $decisionModelBuilder,
+        private readonly EventAppender $eventAppender,
+    ) {
+    }
+
+    #[Handle]
+    public function __invoke(ChangeCourseCapacity $command): void
+    {
+        $state = $this->decisionModelBuilder->build(
+            [
+                'courseExists' => new CourseExists($command->courseId),
+                'courseCapacity' => new CourseCapacityProjection($command->courseId),
+            ],
+        );
+
+        if (!$state['courseExists']) {
+            throw new RuntimeException('Course does not exist');
+        }
+
+        if ($state['courseCapacity'] === $command->capacity) {
+            return;
+        }
+
+        $this->eventAppender->append([
+            new CourseCapacityChanged(
+                $command->courseId,
+                $command->capacity,
+            ),
+        ], $state->appendCondition);
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Handler/DefineCourseHandler.php b/tests/Integration/DynamicConsistencyBoundary/Course/Handler/DefineCourseHandler.php
new file mode 100644
index 00000000..7284e728
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Handler/DefineCourseHandler.php
@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Handler;
+
+use Patchlevel\EventSourcing\Attribute\Handle;
+use Patchlevel\EventSourcing\DCB\DecisionModelBuilder;
+use Patchlevel\EventSourcing\DCB\EventAppender;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Command\DefineCourse;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseDefined;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection\CourseExists;
+use RuntimeException;
+
+final class DefineCourseHandler
+{
+    public function __construct(
+        private readonly DecisionModelBuilder $decisionModelBuilder,
+        private readonly EventAppender $eventAppender,
+    ) {
+    }
+
+    #[Handle]
+    public function __invoke(DefineCourse $command): void
+    {
+        $state = $this->decisionModelBuilder->build(
+            [
+                'courseExists' => new CourseExists($command->courseId),
+            ],
+        );
+
+        if ($state['courseExists']) {
+            throw new RuntimeException('Course already exists');
+        }
+
+        $this->eventAppender->append([
+            new CourseDefined(
+                $command->courseId,
+                $command->capacity,
+            ),
+        ], $state->appendCondition);
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Handler/SubscribeStudentToCourseHandler.php b/tests/Integration/DynamicConsistencyBoundary/Course/Handler/SubscribeStudentToCourseHandler.php
new file mode 100644
index 00000000..f51db248
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Handler/SubscribeStudentToCourseHandler.php
@@ -0,0 +1,66 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Handler;
+
+use Patchlevel\EventSourcing\Attribute\Handle;
+use Patchlevel\EventSourcing\DCB\DecisionModelBuilder;
+use Patchlevel\EventSourcing\DCB\EventAppender;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Command\SubscribeStudentToCourse;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\StudentSubscribedToCourse;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection\CourseCapacityProjection;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection\CourseExists;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection\NumberOfCourseSubscriptionsProjection;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection\NumberOfStudentSubscriptionsProjection;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection\StudentAlreadySubscribedProjection;
+use RuntimeException;
+
+final class SubscribeStudentToCourseHandler
+{
+    public function __construct(
+        private readonly DecisionModelBuilder $decisionModelBuilder,
+        private readonly EventAppender $eventAppender,
+    ) {
+    }
+
+    #[Handle]
+    public function __invoke(SubscribeStudentToCourse $command): void
+    {
+        $state = $this->decisionModelBuilder->build(
+            projections: [
+                'courseExists' => new CourseExists($command->courseId),
+                'courseCapacity' => new CourseCapacityProjection($command->courseId),
+                'numberOfCourseSubscriptions' => new NumberOfCourseSubscriptionsProjection($command->courseId),
+                'numberOfStudentSubscriptions' => new NumberOfStudentSubscriptionsProjection($command->studentId),
+                'studentAlreadySubscribed' => new StudentAlreadySubscribedProjection(
+                    $command->studentId,
+                    $command->courseId,
+                ),
+            ],
+        );
+
+        if (!$state['courseExists']) {
+            throw new RuntimeException("Course {$command->courseId->toString()} does not exist");
+        }
+
+        if ($state['numberOfCourseSubscriptions'] >= $state['courseCapacity']) {
+            throw new RuntimeException("Course {$command->courseId->toString()} is not available");
+        }
+
+        if ($state['studentAlreadySubscribed']) {
+            throw new RuntimeException("Student {$command->studentId->toString()} is already subscribed to course {$command->courseId->toString()}");
+        }
+
+        if ($state['numberOfStudentSubscriptions'] >= 5) {
+            throw new RuntimeException("Student {$command->studentId->toString()} is already subscribed to 5 courses");
+        }
+
+        $this->eventAppender->append([
+            new StudentSubscribedToCourse(
+                $command->studentId,
+                $command->courseId,
+            ),
+        ], $state->appendCondition);
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php
new file mode 100644
index 00000000..d76f62a9
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php
@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
+
+use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\Projection;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseCapacityChanged;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseDefined;
+
+final class CourseCapacityProjection extends Projection
+{
+    public function __construct(
+        private readonly CourseId $courseId,
+    ) {
+    }
+
+    public function initialState(): int
+    {
+        return 0;
+    }
+
+    /** @return list<string> */
+    public function tagFilter(): array
+    {
+        return ["course:{$this->courseId->toString()}"];
+    }
+
+    #[Apply]
+    public function applyCourseDefined(int $state, CourseDefined $event): int
+    {
+        return $event->capacity;
+    }
+
+    #[Apply]
+    public function applyCourseCapacityChanged(int $state, CourseCapacityChanged $event): int
+    {
+        return $event->capacity;
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php
new file mode 100644
index 00000000..4854525e
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php
@@ -0,0 +1,36 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
+
+use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\Projection;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseDefined;
+
+/** @extends Projection<bool> */
+final class CourseExists extends Projection
+{
+    public function __construct(
+        private readonly CourseId $courseId,
+    ) {
+    }
+
+    #[Apply]
+    public function applyCourseDefined(bool $state, CourseDefined $event): bool
+    {
+        return true;
+    }
+
+    /** @return list<string> */
+    public function tagFilter(): array
+    {
+        return ["course:{$this->courseId->toString()}"];
+    }
+
+    public function initialState(): bool
+    {
+        return false;
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php
new file mode 100644
index 00000000..5b37cab1
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php
@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
+
+use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\Projection;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\StudentSubscribedToCourse;
+
+final class NumberOfCourseSubscriptionsProjection extends Projection
+{
+    public function __construct(
+        private readonly CourseId $courseId,
+    ) {
+    }
+
+    #[Apply]
+    public function applyStudentSubscribedToCourse(int $state, StudentSubscribedToCourse $event): int
+    {
+        return $state + 1;
+    }
+
+    public function initialState(): int
+    {
+        return 0;
+    }
+
+    /** @return list<string> */
+    public function tagFilter(): array
+    {
+        return ["course:{$this->courseId->toString()}"];
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php
new file mode 100644
index 00000000..79011691
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php
@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
+
+use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\Projection;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\StudentSubscribedToCourse;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\StudentId;
+
+final class NumberOfStudentSubscriptionsProjection extends Projection
+{
+    public function __construct(
+        private readonly StudentId $studentId,
+    ) {
+    }
+
+    #[Apply]
+    public function applyStudentSubscribedToCourse(int $state, StudentSubscribedToCourse $event): int
+    {
+        return $state + 1;
+    }
+
+    public function initialState(): int
+    {
+        return 0;
+    }
+
+    /** @return list<string> */
+    public function tagFilter(): array
+    {
+        return ["student:{$this->studentId->toString()}"];
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php
new file mode 100644
index 00000000..6f652d46
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php
@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
+
+use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\Projection;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\StudentSubscribedToCourse;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\StudentId;
+
+final class StudentAlreadySubscribedProjection extends Projection
+{
+    public function __construct(
+        private readonly StudentId $studentId,
+        private readonly CourseId $courseId,
+    ) {
+    }
+
+    #[Apply]
+    public function applyStudentSubscribedToCourse(bool $state, StudentSubscribedToCourse $event): bool
+    {
+        return true;
+    }
+
+    public function initialState(): bool
+    {
+        return false;
+    }
+
+    /** @return list<string> */
+    public function tagFilter(): array
+    {
+        return [
+            "student:{$this->studentId->toString()}",
+            "course:{$this->courseId->toString()}",
+        ];
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/StudentId.php b/tests/Integration/DynamicConsistencyBoundary/Course/StudentId.php
new file mode 100644
index 00000000..62d11f76
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/StudentId.php
@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course;
+
+use Patchlevel\EventSourcing\Aggregate\AggregateRootId;
+use Patchlevel\EventSourcing\Aggregate\RamseyUuidV7Behaviour;
+
+final class StudentId implements AggregateRootId
+{
+    use RamseyUuidV7Behaviour;
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php b/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php
new file mode 100644
index 00000000..2e1820ce
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php
@@ -0,0 +1,115 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary;
+
+use Doctrine\DBAL\Connection;
+use Patchlevel\EventSourcing\CommandBus\ServiceHandlerProvider;
+use Patchlevel\EventSourcing\CommandBus\SyncCommandBus;
+use Patchlevel\EventSourcing\DCB\StoreDecisionModelBuilder;
+use Patchlevel\EventSourcing\DCB\StoreEventAppender;
+use Patchlevel\EventSourcing\Message\Serializer\DefaultHeadersSerializer;
+use Patchlevel\EventSourcing\Schema\DoctrineSchemaDirector;
+use Patchlevel\EventSourcing\Serializer\DefaultEventSerializer;
+use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
+use Patchlevel\EventSourcing\Tests\DbalManager;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Command\ChangeCourseCapacity;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Command\DefineCourse;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Command\SubscribeStudentToCourse;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Handler\ChangeCourseCapacityHandler;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Handler\DefineCourseHandler;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Handler\SubscribeStudentToCourseHandler;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\StudentId;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Command\CreateInvoice;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Handler\CreateInvoiceHandler;
+use PHPUnit\Framework\Attributes\CoversNothing;
+use PHPUnit\Framework\TestCase;
+
+#[CoversNothing]
+final class DynamicConsistencyBoundaryTest extends TestCase
+{
+    private Connection $connection;
+
+    public function setUp(): void
+    {
+        $this->connection = DbalManager::createConnection();
+    }
+
+    public function tearDown(): void
+    {
+        $this->connection->close();
+    }
+
+    public function testCourse(): void
+    {
+        $store = new TaggableDoctrineDbalStore(
+            $this->connection,
+            DefaultEventSerializer::createFromPaths([__DIR__ . '/Course/Event']),
+            DefaultHeadersSerializer::createDefault(),
+        );
+
+        $decisionModelBuilder = new StoreDecisionModelBuilder($store);
+        $eventAppender = new StoreEventAppender($store);
+
+        $commandBus = new SyncCommandBus(
+            new ServiceHandlerProvider([
+                new DefineCourseHandler($decisionModelBuilder, $eventAppender),
+                new ChangeCourseCapacityHandler($decisionModelBuilder, $eventAppender),
+                new SubscribeStudentToCourseHandler($decisionModelBuilder, $eventAppender),
+            ]),
+        );
+
+        $schemaDirector = new DoctrineSchemaDirector(
+            $this->connection,
+            $store,
+        );
+
+        $schemaDirector->create();
+
+        $courseId = CourseId::generate();
+        $student1Id = StudentId::generate();
+        $student2Id = StudentId::generate();
+
+        $commandBus->dispatch(new DefineCourse($courseId, 10));
+        $commandBus->dispatch(new ChangeCourseCapacity($courseId, 2));
+        $commandBus->dispatch(new SubscribeStudentToCourse($student1Id, $courseId));
+        $commandBus->dispatch(new SubscribeStudentToCourse($student2Id, $courseId));
+
+        $this->assertTrue(true);
+    }
+
+    public function testInvoice(): void
+    {
+        $store = new TaggableDoctrineDbalStore(
+            $this->connection,
+            DefaultEventSerializer::createFromPaths([__DIR__ . '/Invoice/Event']),
+            DefaultHeadersSerializer::createDefault(),
+        );
+
+        $decisionModelBuilder = new StoreDecisionModelBuilder($store);
+        $eventAppender = new StoreEventAppender($store);
+
+        $commandBus = new SyncCommandBus(
+            new ServiceHandlerProvider([
+                new CreateInvoiceHandler($decisionModelBuilder, $eventAppender),
+            ]),
+        );
+
+        $schemaDirector = new DoctrineSchemaDirector(
+            $this->connection,
+            $store,
+        );
+
+        $schemaDirector->create();
+
+        $commandBus->dispatch(new CreateInvoice(10));
+        $commandBus->dispatch(new CreateInvoice(10));
+        $commandBus->dispatch(new CreateInvoice(10));
+        $commandBus->dispatch(new CreateInvoice(10));
+        $commandBus->dispatch(new CreateInvoice(10));
+
+        $this->assertTrue(true);
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Invoice/Command/CreateInvoice.php b/tests/Integration/DynamicConsistencyBoundary/Invoice/Command/CreateInvoice.php
new file mode 100644
index 00000000..a18ee4c3
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Invoice/Command/CreateInvoice.php
@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Command;
+
+final class CreateInvoice
+{
+    public function __construct(
+        public readonly int $money,
+    ) {
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Invoice/Event/InvoiceCreated.php b/tests/Integration/DynamicConsistencyBoundary/Invoice/Event/InvoiceCreated.php
new file mode 100644
index 00000000..05e03302
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Invoice/Event/InvoiceCreated.php
@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Event;
+
+use Patchlevel\EventSourcing\Attribute\Event;
+use Patchlevel\EventSourcing\Attribute\EventTag;
+
+#[Event('invoice.created')]
+final class InvoiceCreated
+{
+    public function __construct(
+        #[EventTag(prefix: 'invoice')]
+        public readonly int $invoiceNumber,
+        public readonly int $money,
+    ) {
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Invoice/Handler/CreateInvoiceHandler.php b/tests/Integration/DynamicConsistencyBoundary/Invoice/Handler/CreateInvoiceHandler.php
new file mode 100644
index 00000000..aa94e0fd
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Invoice/Handler/CreateInvoiceHandler.php
@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Handler;
+
+use Patchlevel\EventSourcing\Attribute\Handle;
+use Patchlevel\EventSourcing\DCB\DecisionModelBuilder;
+use Patchlevel\EventSourcing\DCB\EventAppender;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Command\CreateInvoice;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Event\InvoiceCreated;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Projection\NextInvoiceNumberProjection;
+
+final class CreateInvoiceHandler
+{
+    public function __construct(
+        private readonly DecisionModelBuilder $decisionModelBuilder,
+        private readonly EventAppender $eventAppender,
+    ) {
+    }
+
+    #[Handle]
+    public function __invoke(CreateInvoice $command): void
+    {
+        $state = $this->decisionModelBuilder->build(
+            [
+                'nextInvoiceNumber' => new NextInvoiceNumberProjection(),
+            ],
+        );
+
+        $this->eventAppender->append([
+            new InvoiceCreated(
+                $state['nextInvoiceNumber'],
+                $command->money,
+            ),
+        ], $state->appendCondition);
+    }
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php b/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
new file mode 100644
index 00000000..6b6d3914
--- /dev/null
+++ b/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Projection;
+
+use Patchlevel\EventSourcing\DCB\Projection;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Event\InvoiceCreated;
+
+final class NextInvoiceNumberProjection extends Projection
+{
+    /** @return list<string> */
+    public function tagFilter(): array
+    {
+        return [];
+    }
+
+    public function initialState(): int
+    {
+        return 1;
+    }
+
+    public function applyInvoiceCreated(int $state, InvoiceCreated $event): int
+    {
+        return $state + 1;
+    }
+}
diff --git a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
index c8b50387..0712545c 100644
--- a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
+++ b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
@@ -7,6 +7,8 @@
 use DateTimeImmutable;
 use Doctrine\DBAL\Connection;
 use Patchlevel\EventSourcing\Clock\FrozenClock;
+use Patchlevel\EventSourcing\DCB\AppendCondition;
+use Patchlevel\EventSourcing\DCB\HighestSequenceNumber;
 use Patchlevel\EventSourcing\Message\Message;
 use Patchlevel\EventSourcing\Schema\DoctrineSchemaDirector;
 use Patchlevel\EventSourcing\Serializer\DefaultEventSerializer;
@@ -20,7 +22,6 @@
 use Patchlevel\EventSourcing\Store\Header\RecordedOnHeader;
 use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
 use Patchlevel\EventSourcing\Store\Header\TagsHeader;
-use Patchlevel\EventSourcing\Store\StreamStore;
 use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
 use Patchlevel\EventSourcing\Store\UniqueConstraintViolation;
 use Patchlevel\EventSourcing\Tests\DbalManager;
@@ -38,7 +39,7 @@
 final class TaggableDoctrineDbalStoreTest extends TestCase
 {
     private Connection $connection;
-    private StreamStore $store;
+    private TaggableDoctrineDbalStore $store;
 
     private ClockInterface $clock;
 
@@ -510,7 +511,7 @@ public function testTags(): void
         try {
             $stream = $this->store->load(
                 new Criteria(
-                    new TagCriterion('profile:' . $profileId1->toString()),
+                    new TagCriterion(['profile:' . $profileId1->toString()], ['test']),
                 ),
             );
 
@@ -532,6 +533,107 @@ public function testTags(): void
         }
     }
 
+    public function testAppend(): void
+    {
+        $profileId1 = ProfileId::generate();
+        $profileId2 = ProfileId::generate();
+
+        $messages = [
+            Message::create(new ProfileCreated($profileId1, 'test'))
+                ->withHeader(new StreamNameHeader('foo'))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+                ->withHeader(new TagsHeader(['profile:' . $profileId1->toString()])),
+            Message::create(new ProfileCreated($profileId2, 'test'))
+                ->withHeader(new StreamNameHeader('foo'))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+                ->withHeader(new TagsHeader(['profile:' . $profileId2->toString()])),
+            Message::create(new ExternEvent('test message'))
+                ->withHeader(new StreamNameHeader('foo'))
+                ->withHeader(new TagsHeader([
+                    'profile:' . $profileId1->toString(),
+                    'profile:' . $profileId2->toString(),
+                ])),
+        ];
+
+        $this->store->append(
+            $messages,
+            new AppendCondition(
+                [],
+                HighestSequenceNumber::none(),
+            ),
+        );
+
+        $stream = null;
+
+        try {
+            $stream = $this->store->load(
+                new Criteria(
+                    new TagCriterion(['profile:' . $profileId1->toString()], ['test']),
+                ),
+            );
+
+            $messages = iterator_to_array($stream);
+
+            self::assertCount(2, $messages);
+
+            self::assertEquals(
+                ['profile:' . $profileId1->toString()],
+                $messages[0]->header(TagsHeader::class)->tags,
+            );
+
+            self::assertEquals(
+                ['profile:' . $profileId1->toString(), 'profile:' . $profileId2->toString()],
+                $messages[1]->header(TagsHeader::class)->tags,
+            );
+        } finally {
+            $stream?->close();
+        }
+    }
+
+    public function testAppendRaceCondition(): void
+    {
+        $profileId1 = ProfileId::generate();
+        $profileId2 = ProfileId::generate();
+
+        $messages = [
+            Message::create(new ProfileCreated($profileId1, 'test'))
+                ->withHeader(new StreamNameHeader('foo'))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+                ->withHeader(new TagsHeader(['profile:' . $profileId1->toString()])),
+            Message::create(new ProfileCreated($profileId2, 'test'))
+                ->withHeader(new StreamNameHeader('foo'))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+                ->withHeader(new TagsHeader(['profile:' . $profileId2->toString()])),
+        ];
+
+        $this->store->append(
+            $messages,
+            new AppendCondition(
+                [],
+                HighestSequenceNumber::none(),
+            ),
+        );
+
+        $messages = [
+            Message::create(new ExternEvent('test message'))
+                ->withHeader(new StreamNameHeader('foo'))
+                ->withHeader(new TagsHeader([
+                    'profile:' . $profileId1->toString(),
+                    'profile:' . $profileId2->toString(),
+                ])),
+        ];
+
+        $this->expectException(UniqueConstraintViolation::class);
+
+        $this->store->append(
+            $messages,
+            new AppendCondition(
+                [['profile:' . $profileId1->toString()]],
+                HighestSequenceNumber::none(),
+            ),
+        );
+    }
+
     public function testStreams(): void
     {
         $profileId = ProfileId::fromString('0190e47e-77e9-7b90-bf62-08bbf0ab9b4b');

From 56ece437ac25e950ccbf7fd6178036ef3da1785a Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Mon, 28 Jul 2025 14:14:51 +0200
Subject: [PATCH 03/22] fix integration tests

---
 src/Store/TaggableDoctrineDbalStore.php | 29 +++++++++----------------
 1 file changed, 10 insertions(+), 19 deletions(-)

diff --git a/src/Store/TaggableDoctrineDbalStore.php b/src/Store/TaggableDoctrineDbalStore.php
index a22125dd..35b06cde 100644
--- a/src/Store/TaggableDoctrineDbalStore.php
+++ b/src/Store/TaggableDoctrineDbalStore.php
@@ -49,7 +49,6 @@
 
 use function array_fill;
 use function array_filter;
-use function array_map;
 use function array_merge;
 use function array_values;
 use function class_exists;
@@ -131,7 +130,7 @@ public function load(
         $builder = $this->connection->createQueryBuilder()
             ->select('*')
             ->from($this->config['table_name'], 'events')
-            ->orderBy('id', $backwards ? 'DESC' : 'ASC');
+            ->orderBy('events.id', $backwards ? 'DESC' : 'ASC');
 
         $this->applyCriteria($builder, $criteria ?? new Criteria());
 
@@ -383,18 +382,18 @@ public function append(iterable $messages, AppendCondition|null $appendCondition
             $parameters = [];
             $types = [];
 
-            $columnsLength = count($columns);
-            //$batchSize = (int)floor(self::MAX_UNSIGNED_SMALL_INT / $columnsLength);
             $position = 0;
 
             foreach ($messages as $message) {
-                $selects[] = sprintf('SELECT %s', implode(', ', array_map(
-                    static fn (string $column) => ':' . $column . $position,
-                    $columns,
-                )));
-
-                /** @var int<0, max> $offset */
-                $offset = $position * $columnsLength;
+                $selects[] = 'SELECT :stream' . $position
+                    . ', :playhead' . $position . ($this->isPostgres ? '::int' : '')
+                    . ', :event_id' . $position
+                    . ', :event_name' . $position
+                    . ', :event_payload' . $position . ($this->isPostgres ? '::jsonb' : '')
+                    . ', :tags' . $position . ($this->isPostgres ? '::jsonb' : '')
+                    . ', :recorded_on' . $position . ($this->isPostgres ? '::timestamptz' : '')
+                    . ', :archived' . $position . ($this->isPostgres ? '::boolean' : '')
+                    . ', :custom_headers' . $position . ($this->isPostgres ? '::jsonb' : '');
 
                 $data = $this->eventSerializer->serialize($message->event());
 
@@ -432,14 +431,6 @@ public function append(iterable $messages, AppendCondition|null $appendCondition
                 $parameters['custom_headers' . $position] = $this->headersSerializer->serialize($this->getCustomHeaders($message));
 
                 $position++;
-
-                /*
-                if ($position !== $batchSize) {
-                    continue;
-                }
-
-                $this->executeSave($columns, $placeholders, $parameters, $types, $this->connection);
-                */
             }
 
             $query = sprintf(

From 092ae15948aba2ad1cae64a8a366fcbc226dfe04 Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Mon, 28 Jul 2025 15:19:29 +0200
Subject: [PATCH 04/22] add benchmark

---
 .../Events/ProfileCreated.php                 |   2 +
 .../SimpleSetupTaggableStoreBench.php         | 145 ++++++++++++++++++
 2 files changed, 147 insertions(+)
 create mode 100644 tests/Benchmark/SimpleSetupTaggableStoreBench.php

diff --git a/tests/Benchmark/BasicImplementation/Events/ProfileCreated.php b/tests/Benchmark/BasicImplementation/Events/ProfileCreated.php
index 7dcea07d..07adcaee 100644
--- a/tests/Benchmark/BasicImplementation/Events/ProfileCreated.php
+++ b/tests/Benchmark/BasicImplementation/Events/ProfileCreated.php
@@ -5,6 +5,7 @@
 namespace Patchlevel\EventSourcing\Tests\Benchmark\BasicImplementation\Events;
 
 use Patchlevel\EventSourcing\Attribute\Event;
+use Patchlevel\EventSourcing\Attribute\EventTag;
 use Patchlevel\EventSourcing\Tests\Benchmark\BasicImplementation\ProfileId;
 use Patchlevel\Hydrator\Attribute\DataSubjectId;
 use Patchlevel\Hydrator\Attribute\PersonalData;
@@ -14,6 +15,7 @@ final class ProfileCreated
 {
     public function __construct(
         #[DataSubjectId]
+        #[EventTag(prefix: 'profile')]
         public ProfileId $profileId,
         public string $name,
         #[PersonalData]
diff --git a/tests/Benchmark/SimpleSetupTaggableStoreBench.php b/tests/Benchmark/SimpleSetupTaggableStoreBench.php
new file mode 100644
index 00000000..8c6da0e1
--- /dev/null
+++ b/tests/Benchmark/SimpleSetupTaggableStoreBench.php
@@ -0,0 +1,145 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Benchmark;
+
+use Patchlevel\EventSourcing\Aggregate\AggregateRootId;
+use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Repository\DefaultRepository;
+use Patchlevel\EventSourcing\Repository\Repository;
+use Patchlevel\EventSourcing\Schema\DoctrineSchemaDirector;
+use Patchlevel\EventSourcing\Serializer\DefaultEventSerializer;
+use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
+use Patchlevel\EventSourcing\Tests\Benchmark\BasicImplementation\Events\ProfileCreated;
+use Patchlevel\EventSourcing\Tests\Benchmark\BasicImplementation\Profile;
+use Patchlevel\EventSourcing\Tests\Benchmark\BasicImplementation\ProfileId;
+use Patchlevel\EventSourcing\Tests\DbalManager;
+use PhpBench\Attributes as Bench;
+
+#[Bench\BeforeMethods('setUp')]
+final class SimpleSetupTaggableStoreBench
+{
+    private TaggableDoctrineDbalStore $store;
+    private Repository $repository;
+
+    private AggregateRootId $singleEventId;
+    private AggregateRootId $multipleEventsId;
+
+    public function setUp(): void
+    {
+        $connection = DbalManager::createConnection();
+
+        $this->store = new TaggableDoctrineDbalStore(
+            $connection,
+            DefaultEventSerializer::createFromPaths([__DIR__ . '/BasicImplementation/Events']),
+        );
+
+        $this->repository = new DefaultRepository($this->store, Profile::metadata());
+
+        $schemaDirector = new DoctrineSchemaDirector(
+            $connection,
+            $this->store,
+        );
+
+        $schemaDirector->create();
+
+        $this->singleEventId = ProfileId::generate();
+        $profile = Profile::create($this->singleEventId, 'Peter');
+        $this->repository->save($profile);
+
+        $this->multipleEventsId = ProfileId::generate();
+        $profile = Profile::create($this->multipleEventsId, 'Peter');
+
+        for ($i = 0; $i < 10_000; $i++) {
+            $profile->changeName('Peter');
+        }
+
+        $this->repository->save($profile);
+    }
+
+    #[Bench\Revs(10)]
+    public function benchLoad1Event(): void
+    {
+        $this->repository->load($this->singleEventId);
+    }
+
+    #[Bench\Revs(10)]
+    public function benchLoad10000Events(): void
+    {
+        $this->repository->load($this->multipleEventsId);
+    }
+
+    #[Bench\Revs(10)]
+    public function benchSave1Event(): void
+    {
+        $profile = Profile::create(ProfileId::generate(), 'Peter');
+        $this->repository->save($profile);
+    }
+
+    #[Bench\Revs(10)]
+    public function benchSave10000Events(): void
+    {
+        $profile = Profile::create(ProfileId::generate(), 'Peter');
+
+        for ($i = 1; $i < 10_000; $i++) {
+            $profile->changeName('Peter');
+        }
+
+        $this->repository->save($profile);
+    }
+
+    #[Bench\Revs(1)]
+    public function benchSave10000Aggregates(): void
+    {
+        for ($i = 1; $i < 10_000; $i++) {
+            $profile = Profile::create(ProfileId::generate(), 'Peter');
+            $this->repository->save($profile);
+        }
+    }
+
+    #[Bench\Revs(10)]
+    public function benchSave10000AggregatesTransaction(): void
+    {
+        $this->store->transactional(function (): void {
+            for ($i = 1; $i < 10_000; $i++) {
+                $profile = Profile::create(ProfileId::generate(), 'Peter');
+                $this->repository->save($profile);
+            }
+        });
+    }
+
+    #[Bench\Revs(10)]
+    public function benchAppend1Event(): void
+    {
+        $messages = [
+            Message::create(
+                new ProfileCreated(
+                    ProfileId::generate(),
+                    'Peter',
+                    null,
+                )
+            )
+        ];
+
+        $this->store->append($messages);
+    }
+
+    #[Bench\Revs(10)]
+    public function benchAppend100Events(): void
+    {
+        $messages = [];
+
+        for ($i = 1; $i < 100; $i++) {
+            $messages[] = Message::create(
+                new ProfileCreated(
+                    ProfileId::generate(),
+                    'Peter',
+                    null,
+                )
+            );
+        }
+
+        $this->store->append($messages);
+    }
+}

From 2906ccb03b6285f118036ce4c491eb05d040b4b0 Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Tue, 29 Jul 2025 16:33:36 +0200
Subject: [PATCH 05/22] refactoring

---
 Makefile                                      |  2 +-
 docs/mkdocs.yml                               |  1 +
 src/Attribute/EventTag.php                    |  1 +
 src/DCB/AppendCondition.php                   |  2 +-
 src/DCB/AttributeEventTagExtractor.php        | 10 +++-
 src/DCB/HighestSequenceNumber.php             | 24 --------
 src/DCB/Projection.php                        | 42 +++++++++++++
 src/DCB/StoreDecisionModelBuilder.php         |  2 +-
 .../Translator/ExtractEventTagTranslator.php  | 32 ++++++++++
 .../MessageDecorator/EventTagDecorator.php    |  1 +
 src/Store/TaggableDoctrineDbalStore.php       |  6 +-
 .../SimpleSetupTaggableStoreBench.php         |  6 +-
 .../Store/TaggableDoctrineDbalStoreTest.php   | 13 +---
 .../DCB/AttributeEventTagExtractorTest.php    | 60 +++++++++++++++++++
 14 files changed, 158 insertions(+), 44 deletions(-)
 delete mode 100644 src/DCB/HighestSequenceNumber.php
 create mode 100644 src/Message/Translator/ExtractEventTagTranslator.php
 create mode 100644 tests/Unit/DCB/AttributeEventTagExtractorTest.php

diff --git a/Makefile b/Makefile
index 4f9b56d6..859c0b31 100644
--- a/Makefile
+++ b/Makefile
@@ -74,7 +74,7 @@ test: phpunit
 
 .PHONY: benchmark
 benchmark: vendor                                                               ## run benchmarks
-	DB_URL=sqlite3:///:memory: php -d memory_limit=512M vendor/bin/phpbench run tests/Benchmark --report=default
+	DB_URL=sqlite3:///:memory: php -d memory_limit=512M vendor/bin/phpbench run tests/Benchmark --report=default --filter=benchAppend100Events
 
 .PHONY: benchmark-base
 benchmark-base: vendor                                                   	## run benchmarks
diff --git a/docs/mkdocs.yml b/docs/mkdocs.yml
index 342d3913..0cbac3c1 100644
--- a/docs/mkdocs.yml
+++ b/docs/mkdocs.yml
@@ -101,6 +101,7 @@ nav:
     - Event Bus:  event_bus.md
     - Query Bus:  query_bus.md
   - Advanced:
+    - Dynamic Consistency Boundary: dynamic_consistency_boundary.md
     - Identifier: identifier.md
     - Normalizer: normalizer.md
     - Snapshots: snapshots.md
diff --git a/src/Attribute/EventTag.php b/src/Attribute/EventTag.php
index e2506fcc..9e05dce7 100644
--- a/src/Attribute/EventTag.php
+++ b/src/Attribute/EventTag.php
@@ -11,6 +11,7 @@ final class EventTag
 {
     public function __construct(
         public readonly string|null $prefix = null,
+        public readonly string|null $hash = null,
     ) {
     }
 }
diff --git a/src/DCB/AppendCondition.php b/src/DCB/AppendCondition.php
index 51f7cbfe..20c5a36f 100644
--- a/src/DCB/AppendCondition.php
+++ b/src/DCB/AppendCondition.php
@@ -10,7 +10,7 @@ final class AppendCondition
     /** @param list<list<string>> $tags */
     public function __construct(
         public readonly array $tags,
-        public readonly HighestSequenceNumber|null $expectedHighestSequenceNumber = null,
+        public readonly int|null $highestSequenceNumber = null,
     ) {
     }
 }
diff --git a/src/DCB/AttributeEventTagExtractor.php b/src/DCB/AttributeEventTagExtractor.php
index 49618d4a..b19d2cce 100644
--- a/src/DCB/AttributeEventTagExtractor.php
+++ b/src/DCB/AttributeEventTagExtractor.php
@@ -11,6 +11,7 @@
 
 use function array_keys;
 use function get_debug_type;
+use function hash;
 use function is_int;
 use function is_string;
 use function sprintf;
@@ -32,6 +33,7 @@ public function extract(object $event): array
                 continue;
             }
 
+            /** @var EventTag $attribute */
             $attribute = $attributes[0]->newInstance();
 
             $value = $property->getValue($event);
@@ -46,11 +48,17 @@ public function extract(object $event): array
                 );
             }
 
+            $value = (string)$value;
+
+            if ($attribute->hash) {
+                $value = hash($attribute->hash, $value);
+            }
+
             if ($attribute->prefix) {
                 $value = $attribute->prefix . ':' . $value;
             }
 
-            $tags[(string)$value] = true;
+            $tags[$value] = true;
         }
 
         return array_keys($tags);
diff --git a/src/DCB/HighestSequenceNumber.php b/src/DCB/HighestSequenceNumber.php
deleted file mode 100644
index 9d863f65..00000000
--- a/src/DCB/HighestSequenceNumber.php
+++ /dev/null
@@ -1,24 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Patchlevel\EventSourcing\DCB;
-
-/** @experimental */
-final class HighestSequenceNumber
-{
-    public function __construct(
-        public readonly int $value,
-    ) {
-    }
-
-    public static function none(): self
-    {
-        return new self(0);
-    }
-
-    public function isNone(): bool
-    {
-        return $this->value === 0;
-    }
-}
diff --git a/src/DCB/Projection.php b/src/DCB/Projection.php
index 6ab922da..099c4dc1 100644
--- a/src/DCB/Projection.php
+++ b/src/DCB/Projection.php
@@ -4,10 +4,15 @@
 
 namespace Patchlevel\EventSourcing\DCB;
 
+use Closure;
+use Patchlevel\EventSourcing\Attribute\Apply;
 use Patchlevel\EventSourcing\Message\Message;
 use ReflectionClass;
+use RuntimeException;
 
+use function is_a;
 use function method_exists;
+use function sprintf;
 
 /**
  * @experimental
@@ -38,4 +43,41 @@ public function apply(mixed $state, Message $message): mixed
 
         return $state;
     }
+
+    /** @return array<class-string, Closure(mixed, object): mixed> */
+    private static function applies(): array
+    {
+        $reflection = new ReflectionClass(static::class);
+        $methods = $reflection->getMethods();
+
+        $applies = [];
+
+        foreach ($methods as $method) {
+            $attributes = $method->getAttributes(Apply::class);
+
+            if ($attributes === []) {
+                continue;
+            }
+
+            foreach ($attributes as $attribute) {
+                /** @var Apply $apply */
+                $apply = $attribute->newInstance();
+
+                if ($apply->class === null) {
+                    $applies[$method->getName()] = Closure::fromCallable([$reflection->getName(), $method->getName()]);
+                    continue;
+                }
+
+                if (!is_a($apply->class, static::class, true)) {
+                    throw new RuntimeException(
+                        sprintf('Apply class %s must be a subclass of %s', $apply->class, static::class),
+                    );
+                }
+
+                $applies[$apply->class] = Closure::fromCallable([$reflection->getName(), $method->getName()]);
+            }
+        }
+
+        return $applies;
+    }
 }
diff --git a/src/DCB/StoreDecisionModelBuilder.php b/src/DCB/StoreDecisionModelBuilder.php
index f7d2b0b5..c772cac8 100644
--- a/src/DCB/StoreDecisionModelBuilder.php
+++ b/src/DCB/StoreDecisionModelBuilder.php
@@ -43,7 +43,7 @@ public function build(
             $state,
             new AppendCondition(
                 $projection->groupedTagFilter(),
-                new HighestSequenceNumber($highestId ?? 0),
+                $highestId ?? 0,
             ),
         );
     }
diff --git a/src/Message/Translator/ExtractEventTagTranslator.php b/src/Message/Translator/ExtractEventTagTranslator.php
new file mode 100644
index 00000000..9d5c3f0d
--- /dev/null
+++ b/src/Message/Translator/ExtractEventTagTranslator.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Message\Translator;
+
+use Patchlevel\EventSourcing\DCB\AttributeEventTagExtractor;
+use Patchlevel\EventSourcing\DCB\EventTagExtractor;
+use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Store\Header\TagsHeader;
+
+/** @experimental */
+final class ExtractEventTagTranslator implements Translator
+{
+    public function __construct(
+        private readonly EventTagExtractor $eventTagExtractor = new AttributeEventTagExtractor(),
+        private readonly bool $skipAlreadyTagged = false,
+    ) {
+    }
+
+    /** @return list<Message> */
+    public function __invoke(Message $message): array
+    {
+        if ($this->skipAlreadyTagged && $message->hasHeader(TagsHeader::class)) {
+            return [$message];
+        }
+
+        $tags = $this->eventTagExtractor->extract($message->event());
+
+        return [$message->withHeader(new TagsHeader($tags))];
+    }
+}
diff --git a/src/Repository/MessageDecorator/EventTagDecorator.php b/src/Repository/MessageDecorator/EventTagDecorator.php
index 9b97b565..40680d69 100644
--- a/src/Repository/MessageDecorator/EventTagDecorator.php
+++ b/src/Repository/MessageDecorator/EventTagDecorator.php
@@ -9,6 +9,7 @@
 use Patchlevel\EventSourcing\Message\Message;
 use Patchlevel\EventSourcing\Store\Header\TagsHeader;
 
+/** @experimental */
 final class EventTagDecorator implements MessageDecorator
 {
     public function __construct(
diff --git a/src/Store/TaggableDoctrineDbalStore.php b/src/Store/TaggableDoctrineDbalStore.php
index 35b06cde..1ae0c509 100644
--- a/src/Store/TaggableDoctrineDbalStore.php
+++ b/src/Store/TaggableDoctrineDbalStore.php
@@ -449,11 +449,11 @@ public function append(iterable $messages, AppendCondition|null $appendCondition
 
                 $this->queryCondition($queryBuilder, $appendCondition->tags);
 
-                if ($appendCondition->expectedHighestSequenceNumber->isNone()) {
+                if ($appendCondition->highestSequenceNumber === 0) {
                     $query .= ' WHERE NOT EXISTS (' . $queryBuilder->getSQL() . ')';
                 } else {
                     $query .= ' WHERE (' . $queryBuilder->getSQL() . ') = :highestId';
-                    $parameters['highestId'] = $appendCondition->expectedHighestSequenceNumber->value;
+                    $parameters['highestId'] = $appendCondition->highestSequenceNumber;
                 }
 
                 $parameters = array_merge(
@@ -470,7 +470,7 @@ public function append(iterable $messages, AppendCondition|null $appendCondition
             try {
                 $affectedRows = $this->connection->executeStatement($query, $parameters, $types);
 
-                if ($affectedRows === 0 && $appendCondition->expectedHighestSequenceNumber !== null) {
+                if ($affectedRows === 0 && $appendCondition->highestSequenceNumber !== null) {
                     throw new UniqueConstraintViolation();
                 }
             } catch (UniqueConstraintViolationException $e) {
diff --git a/tests/Benchmark/SimpleSetupTaggableStoreBench.php b/tests/Benchmark/SimpleSetupTaggableStoreBench.php
index 8c6da0e1..c5c929b7 100644
--- a/tests/Benchmark/SimpleSetupTaggableStoreBench.php
+++ b/tests/Benchmark/SimpleSetupTaggableStoreBench.php
@@ -118,8 +118,8 @@ public function benchAppend1Event(): void
                     ProfileId::generate(),
                     'Peter',
                     null,
-                )
-            )
+                ),
+            ),
         ];
 
         $this->store->append($messages);
@@ -136,7 +136,7 @@ public function benchAppend100Events(): void
                     ProfileId::generate(),
                     'Peter',
                     null,
-                )
+                ),
             );
         }
 
diff --git a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
index 0712545c..4a3f3e0e 100644
--- a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
+++ b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
@@ -8,7 +8,6 @@
 use Doctrine\DBAL\Connection;
 use Patchlevel\EventSourcing\Clock\FrozenClock;
 use Patchlevel\EventSourcing\DCB\AppendCondition;
-use Patchlevel\EventSourcing\DCB\HighestSequenceNumber;
 use Patchlevel\EventSourcing\Message\Message;
 use Patchlevel\EventSourcing\Schema\DoctrineSchemaDirector;
 use Patchlevel\EventSourcing\Serializer\DefaultEventSerializer;
@@ -557,10 +556,7 @@ public function testAppend(): void
 
         $this->store->append(
             $messages,
-            new AppendCondition(
-                [],
-                HighestSequenceNumber::none(),
-            ),
+            new AppendCondition([], 0),
         );
 
         $stream = null;
@@ -608,10 +604,7 @@ public function testAppendRaceCondition(): void
 
         $this->store->append(
             $messages,
-            new AppendCondition(
-                [],
-                HighestSequenceNumber::none(),
-            ),
+            new AppendCondition([], 0),
         );
 
         $messages = [
@@ -629,7 +622,7 @@ public function testAppendRaceCondition(): void
             $messages,
             new AppendCondition(
                 [['profile:' . $profileId1->toString()]],
-                HighestSequenceNumber::none(),
+                0,
             ),
         );
     }
diff --git a/tests/Unit/DCB/AttributeEventTagExtractorTest.php b/tests/Unit/DCB/AttributeEventTagExtractorTest.php
new file mode 100644
index 00000000..ce94bb3b
--- /dev/null
+++ b/tests/Unit/DCB/AttributeEventTagExtractorTest.php
@@ -0,0 +1,60 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Unit\DCB;
+
+use Patchlevel\EventSourcing\Attribute\EventTag;
+use Patchlevel\EventSourcing\DCB\AttributeEventTagExtractor;
+use PHPUnit\Framework\TestCase;
+
+class AttributeEventTagExtractorTest extends TestCase
+{
+    public function testExtractEmpty(): void
+    {
+        $extractor = new AttributeEventTagExtractor();
+
+        $event = new class {
+        };
+
+        $tags = $extractor->extract($event);
+
+        self::assertSame([], $tags);
+    }
+
+    public function testExtract(): void
+    {
+        $extractor = new AttributeEventTagExtractor();
+
+        $event = new class ('foo') {
+            public function __construct(
+                #[EventTag]
+                public string $id,
+                #[EventTag(prefix: 'bar')]
+                public string $name = 'baz',
+            ) {
+            }
+        };
+
+        $tags = $extractor->extract($event);
+
+        self::assertSame(['foo', 'bar:baz'], $tags);
+    }
+
+    public function testExtractWithHash(): void
+    {
+        $extractor = new AttributeEventTagExtractor();
+
+        $event = new class ('foo') {
+            public function __construct(
+                #[EventTag(prefix: 'name', hash: 'sha1')]
+                public string $name,
+            ) {
+            }
+        };
+
+        $tags = $extractor->extract($event);
+
+        self::assertSame(['name:0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33'], $tags);
+    }
+}

From 82e8251a403369ec5ef58c2b5ba4b28cce120c87 Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Wed, 30 Jul 2025 10:27:18 +0200
Subject: [PATCH 06/22] handle stringable in AttributeEventTagExtractor

---
 src/DCB/AttributeEventTagExtractor.php | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/DCB/AttributeEventTagExtractor.php b/src/DCB/AttributeEventTagExtractor.php
index b19d2cce..4b54c063 100644
--- a/src/DCB/AttributeEventTagExtractor.php
+++ b/src/DCB/AttributeEventTagExtractor.php
@@ -8,6 +8,7 @@
 use Patchlevel\EventSourcing\Attribute\EventTag;
 use ReflectionClass;
 use RuntimeException;
+use Stringable;
 
 use function array_keys;
 use function get_debug_type;
@@ -42,14 +43,16 @@ public function extract(object $event): array
                 $value = $value->toString();
             }
 
-            if (!is_string($value) && !is_int($value)) {
+            if ($value instanceof Stringable || is_int($value)) {
+                $value = (string)$value;
+            }
+
+            if (!is_string($value)) {
                 throw new RuntimeException(
-                    sprintf('Event tag value must be a string or an int, %s given', get_debug_type($value)),
+                    sprintf('Event tag value must be stringable, %s given', get_debug_type($value)),
                 );
             }
 
-            $value = (string)$value;
-
             if ($attribute->hash) {
                 $value = hash($attribute->hash, $value);
             }

From 776769041c59e48fcdc993d41aae7ab287126646 Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Wed, 30 Jul 2025 16:02:44 +0200
Subject: [PATCH 07/22] add Query value object

---
 src/DCB/CompositeProjection.php               |  2 +-
 src/DCB/DecisionModel.php                     |  1 +
 src/DCB/EventAppender.php                     |  2 +
 src/DCB/StoreDecisionModelBuilder.php         | 26 ++++----
 src/DCB/StoreEventAppender.php                |  5 +-
 src/{DCB => Store}/AppendCondition.php        |  5 +-
 src/Store/AppendConditionNotMet.php           | 14 +++++
 src/Store/AppendStore.php                     | 18 ++++++
 src/Store/Criteria/TagCriterion.php           | 10 +--
 src/Store/Query.php                           | 17 +++++
 src/Store/QueryComponent.php                  | 14 +++++
 src/Store/TaggableDoctrineDbalStore.php       | 63 ++++++++++++++-----
 .../Store/TaggableDoctrineDbalStoreTest.php   | 31 ++++-----
 13 files changed, 149 insertions(+), 59 deletions(-)
 rename src/{DCB => Store}/AppendCondition.php (62%)
 create mode 100644 src/Store/AppendConditionNotMet.php
 create mode 100644 src/Store/AppendStore.php
 create mode 100644 src/Store/Query.php
 create mode 100644 src/Store/QueryComponent.php

diff --git a/src/DCB/CompositeProjection.php b/src/DCB/CompositeProjection.php
index 628c9726..82e3c926 100644
--- a/src/DCB/CompositeProjection.php
+++ b/src/DCB/CompositeProjection.php
@@ -19,7 +19,7 @@
  * @experimental
  * @extends Projection<array<string, mixed>>
  */
-final class CompositeProjection extends Projection
+final class CompositeProjection
 {
     /** @param array<string, Projection> $projections */
     public function __construct(
diff --git a/src/DCB/DecisionModel.php b/src/DCB/DecisionModel.php
index 5de31669..54fb942a 100644
--- a/src/DCB/DecisionModel.php
+++ b/src/DCB/DecisionModel.php
@@ -7,6 +7,7 @@
 use ArrayAccess;
 use LogicException;
 use OutOfBoundsException;
+use Patchlevel\EventSourcing\Store\AppendCondition;
 
 use function array_key_exists;
 
diff --git a/src/DCB/EventAppender.php b/src/DCB/EventAppender.php
index 3e3c19ec..b0bc4cad 100644
--- a/src/DCB/EventAppender.php
+++ b/src/DCB/EventAppender.php
@@ -4,6 +4,8 @@
 
 namespace Patchlevel\EventSourcing\DCB;
 
+use Patchlevel\EventSourcing\Store\AppendCondition;
+
 /** @experimental */
 interface EventAppender
 {
diff --git a/src/DCB/StoreDecisionModelBuilder.php b/src/DCB/StoreDecisionModelBuilder.php
index c772cac8..49f824de 100644
--- a/src/DCB/StoreDecisionModelBuilder.php
+++ b/src/DCB/StoreDecisionModelBuilder.php
@@ -4,16 +4,18 @@
 
 namespace Patchlevel\EventSourcing\DCB;
 
-use Patchlevel\EventSourcing\Store\Criteria\Criteria;
-use Patchlevel\EventSourcing\Store\Criteria\StreamCriterion;
-use Patchlevel\EventSourcing\Store\Criteria\TagCriterion;
-use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
+use Patchlevel\EventSourcing\Store\AppendCondition;
+use Patchlevel\EventSourcing\Store\AppendStore;
+use Patchlevel\EventSourcing\Store\Query;
+use Patchlevel\EventSourcing\Store\QueryComponent;
+
+use function array_map;
 
 /** @experimental */
 final class StoreDecisionModelBuilder implements DecisionModelBuilder
 {
     public function __construct(
-        private TaggableDoctrineDbalStore $store,
+        private AppendStore $store,
     ) {
     }
 
@@ -23,12 +25,12 @@ public function build(
     ): DecisionModel {
         $projection = new CompositeProjection($projections);
 
-        $stream = $this->store->load(
-            new Criteria(
-                new StreamCriterion('main'),
-                new TagCriterion(...$projection->groupedTagFilter()),
-            ),
-        );
+        $query = new Query(...array_map(
+            static fn (array $tags) => new QueryComponent($tags),
+            $projection->groupedTagFilter(),
+        ));
+
+        $stream = $this->store->query($query);
 
         $state = $projection->initialState();
 
@@ -42,7 +44,7 @@ public function build(
         return new DecisionModel(
             $state,
             new AppendCondition(
-                $projection->groupedTagFilter(),
+                $query,
                 $highestId ?? 0,
             ),
         );
diff --git a/src/DCB/StoreEventAppender.php b/src/DCB/StoreEventAppender.php
index c36f516e..cf7b1b0c 100644
--- a/src/DCB/StoreEventAppender.php
+++ b/src/DCB/StoreEventAppender.php
@@ -5,9 +5,10 @@
 namespace Patchlevel\EventSourcing\DCB;
 
 use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Store\AppendCondition;
+use Patchlevel\EventSourcing\Store\AppendStore;
 use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
 use Patchlevel\EventSourcing\Store\Header\TagsHeader;
-use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
 
 use function array_map;
 
@@ -15,7 +16,7 @@
 final class StoreEventAppender implements EventAppender
 {
     public function __construct(
-        private readonly TaggableDoctrineDbalStore $store,
+        private readonly AppendStore $store,
         private readonly EventTagExtractor $eventTagExtractor = new AttributeEventTagExtractor(),
     ) {
     }
diff --git a/src/DCB/AppendCondition.php b/src/Store/AppendCondition.php
similarity index 62%
rename from src/DCB/AppendCondition.php
rename to src/Store/AppendCondition.php
index 20c5a36f..53797ae4 100644
--- a/src/DCB/AppendCondition.php
+++ b/src/Store/AppendCondition.php
@@ -2,14 +2,13 @@
 
 declare(strict_types=1);
 
-namespace Patchlevel\EventSourcing\DCB;
+namespace Patchlevel\EventSourcing\Store;
 
 /** @experimental */
 final class AppendCondition
 {
-    /** @param list<list<string>> $tags */
     public function __construct(
-        public readonly array $tags,
+        public readonly Query $query,
         public readonly int|null $highestSequenceNumber = null,
     ) {
     }
diff --git a/src/Store/AppendConditionNotMet.php b/src/Store/AppendConditionNotMet.php
new file mode 100644
index 00000000..fd040264
--- /dev/null
+++ b/src/Store/AppendConditionNotMet.php
@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Store;
+
+class AppendConditionNotMet extends StoreException
+{
+    public function __construct(
+        public readonly AppendCondition $appendCondition,
+    ) {
+        parent::__construct('Append condition not met');
+    }
+}
diff --git a/src/Store/AppendStore.php b/src/Store/AppendStore.php
new file mode 100644
index 00000000..cfa31e53
--- /dev/null
+++ b/src/Store/AppendStore.php
@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Store;
+
+use Patchlevel\EventSourcing\Message\Message;
+
+interface AppendStore
+{
+    /** @param iterable<Message> $messages */
+    public function append(
+        iterable $messages,
+        AppendCondition|null $appendCondition = null,
+    ): void;
+
+    public function query(Query $query): Stream;
+}
diff --git a/src/Store/Criteria/TagCriterion.php b/src/Store/Criteria/TagCriterion.php
index b4f3692c..b973745f 100644
--- a/src/Store/Criteria/TagCriterion.php
+++ b/src/Store/Criteria/TagCriterion.php
@@ -4,18 +4,12 @@
 
 namespace Patchlevel\EventSourcing\Store\Criteria;
 
-use function array_values;
-
 /** @experimental */
 final class TagCriterion
 {
-    /** @var list<list<string>> */
-    public readonly array $tags;
-
-    /** @param list<string> ...$tags */
+    /** @param list<string> $tags */
     public function __construct(
-        array ...$tags,
+        public readonly array $tags,
     ) {
-        $this->tags = array_values($tags);
     }
 }
diff --git a/src/Store/Query.php b/src/Store/Query.php
new file mode 100644
index 00000000..07ce1d68
--- /dev/null
+++ b/src/Store/Query.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Store;
+
+final class Query
+{
+    /** @var list<QueryComponent> */
+    public readonly array $components;
+
+    public function __construct(
+        QueryComponent ...$components,
+    ) {
+        $this->components = $components;
+    }
+}
diff --git a/src/Store/QueryComponent.php b/src/Store/QueryComponent.php
new file mode 100644
index 00000000..b8713582
--- /dev/null
+++ b/src/Store/QueryComponent.php
@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Store;
+
+final class QueryComponent
+{
+    /** @param list<string> $tags */
+    public function __construct(
+        public readonly array $tags,
+    ) {
+    }
+}
diff --git a/src/Store/TaggableDoctrineDbalStore.php b/src/Store/TaggableDoctrineDbalStore.php
index 1ae0c509..bd44c3b0 100644
--- a/src/Store/TaggableDoctrineDbalStore.php
+++ b/src/Store/TaggableDoctrineDbalStore.php
@@ -19,7 +19,6 @@
 use Doctrine\DBAL\Types\Type;
 use Doctrine\DBAL\Types\Types;
 use Patchlevel\EventSourcing\Clock\SystemClock;
-use Patchlevel\EventSourcing\DCB\AppendCondition;
 use Patchlevel\EventSourcing\Message\HeaderNotFound;
 use Patchlevel\EventSourcing\Message\Message;
 use Patchlevel\EventSourcing\Message\Serializer\DefaultHeadersSerializer;
@@ -65,7 +64,7 @@
 use function str_replace;
 
 /** @experimental */
-final class TaggableDoctrineDbalStore implements StreamStore, SubscriptionStore, DoctrineSchemaConfigurator
+final class TaggableDoctrineDbalStore implements StreamStore, AppendStore, SubscriptionStore, DoctrineSchemaConfigurator
 {
     /**
      * PostgreSQL has a limit of 65535 parameters in a single query.
@@ -129,8 +128,8 @@ public function load(
     ): TaggableDoctrineDbalStoreStream {
         $builder = $this->connection->createQueryBuilder()
             ->select('*')
-            ->from($this->config['table_name'], 'events')
-            ->orderBy('events.id', $backwards ? 'DESC' : 'ASC');
+            ->from($this->config['table_name'])
+            ->orderBy('id', $backwards ? 'DESC' : 'ASC');
 
         $this->applyCriteria($builder, $criteria ?? new Criteria());
 
@@ -229,7 +228,17 @@ private function applyCriteria(QueryBuilder $builder, Criteria $criteria): void
                     $builder->setParameter('event_id', $criterion->eventId, ArrayParameterType::STRING);
                     break;
                 case TagCriterion::class:
-                    $this->queryCondition($builder, $criterion->tags);
+                    if ($this->isSQLite) {
+                        $builder->andWhere('NOT EXISTS(SELECT value FROM JSON_EACH(:tags) WHERE value NOT IN (SELECT value FROM JSON_EACH(tags)))');
+                    } elseif ($this->isPostgres) {
+                        $builder->andWhere('tags @> :tags::jsonb');
+                    } elseif ($this->isMysql || $this->isMariaDb) {
+                        $builder->andWhere('JSON_CONTAINS(tags, :tags)');
+                    } else {
+                        throw new RuntimeException('x');
+                    }
+
+                    $builder->setParameter('tags', json_encode($criterion->tags));
                     break;
                 default:
                     throw new UnsupportedCriterion($criterion::class);
@@ -440,14 +449,14 @@ public function append(iterable $messages, AppendCondition|null $appendCondition
                 implode(' UNION ALL ', $selects),
             );
 
-            if ($appendCondition instanceof AppendCondition && $appendCondition->tags !== []) {
+            if ($appendCondition instanceof AppendCondition && $appendCondition->query->components !== []) {
                 $queryBuilder = $this->connection->createQueryBuilder()
                     ->select('events.id')
                     ->from($this->config['table_name'], 'events')
                     ->orderBy('events.id', 'DESC')
                     ->setMaxResults(1);
 
-                $this->queryCondition($queryBuilder, $appendCondition->tags);
+                $this->queryCondition($queryBuilder, $appendCondition->query);
 
                 if ($appendCondition->highestSequenceNumber === 0) {
                     $query .= ' WHERE NOT EXISTS (' . $queryBuilder->getSQL() . ')';
@@ -469,16 +478,37 @@ public function append(iterable $messages, AppendCondition|null $appendCondition
 
             try {
                 $affectedRows = $this->connection->executeStatement($query, $parameters, $types);
-
-                if ($affectedRows === 0 && $appendCondition->highestSequenceNumber !== null) {
-                    throw new UniqueConstraintViolation();
-                }
             } catch (UniqueConstraintViolationException $e) {
                 throw new UniqueConstraintViolation($e);
             }
+
+            if ($affectedRows === 0 && $appendCondition->highestSequenceNumber !== null) {
+                throw new AppendConditionNotMet($appendCondition);
+            }
         });
     }
 
+    public function query(Query $query): Stream
+    {
+        $builder = $this->connection->createQueryBuilder()
+            ->select('*')
+            ->from($this->config['table_name'], 'events')
+            ->orderBy('events.id', 'ASC');
+
+        $this->queryCondition($builder, $query);
+
+        return new TaggableDoctrineDbalStoreStream(
+            $this->connection->executeQuery(
+                $builder->getSQL(),
+                $builder->getParameters(),
+                $builder->getParameterTypes(),
+            ),
+            $this->eventSerializer,
+            $this->headersSerializer,
+            $this->connection->getDatabasePlatform(),
+        );
+    }
+
     /**
      * @param Closure():ClosureReturn $function
      *
@@ -775,14 +805,17 @@ private function uniqueParameterGenerator(): Closure
         };
     }
 
-    /** @param list<list<string>> $tagGroups */
-    private function queryCondition(QueryBuilder $builder, array $tagGroups): void
+    private function queryCondition(QueryBuilder $builder, Query $query): void
     {
+        if ($query->components === []) {
+            return;
+        }
+
         $subqueries = [];
 
         $uniqueParameterGenerator = $this->uniqueParameterGenerator();
 
-        foreach ($tagGroups as $tags) {
+        foreach ($query->components as $component) {
             $subQueryBuilder = $this->connection->createQueryBuilder()
                 ->select('id')
                 ->from($this->config['table_name']);
@@ -799,7 +832,7 @@ private function queryCondition(QueryBuilder $builder, array $tagGroups): void
                 throw new RuntimeException('x');
             }
 
-            $builder->setParameter($parameterName, json_encode($tags));
+            $builder->setParameter($parameterName, json_encode($component->tags));
 
             $subqueries[] = $subQueryBuilder->getSQL();
         }
diff --git a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
index 4a3f3e0e..1cd7c6fe 100644
--- a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
+++ b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
@@ -7,10 +7,11 @@
 use DateTimeImmutable;
 use Doctrine\DBAL\Connection;
 use Patchlevel\EventSourcing\Clock\FrozenClock;
-use Patchlevel\EventSourcing\DCB\AppendCondition;
 use Patchlevel\EventSourcing\Message\Message;
 use Patchlevel\EventSourcing\Schema\DoctrineSchemaDirector;
 use Patchlevel\EventSourcing\Serializer\DefaultEventSerializer;
+use Patchlevel\EventSourcing\Store\AppendCondition;
+use Patchlevel\EventSourcing\Store\AppendConditionNotMet;
 use Patchlevel\EventSourcing\Store\Criteria\Criteria;
 use Patchlevel\EventSourcing\Store\Criteria\StreamCriterion;
 use Patchlevel\EventSourcing\Store\Criteria\TagCriterion;
@@ -21,6 +22,8 @@
 use Patchlevel\EventSourcing\Store\Header\RecordedOnHeader;
 use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
 use Patchlevel\EventSourcing\Store\Header\TagsHeader;
+use Patchlevel\EventSourcing\Store\Query;
+use Patchlevel\EventSourcing\Store\QueryComponent;
 use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
 use Patchlevel\EventSourcing\Store\UniqueConstraintViolation;
 use Patchlevel\EventSourcing\Tests\DbalManager;
@@ -510,7 +513,7 @@ public function testTags(): void
         try {
             $stream = $this->store->load(
                 new Criteria(
-                    new TagCriterion(['profile:' . $profileId1->toString()], ['test']),
+                    new TagCriterion(['profile:' . $profileId1->toString()]),
                 ),
             );
 
@@ -532,7 +535,7 @@ public function testTags(): void
         }
     }
 
-    public function testAppend(): void
+    public function testAppendAndQuery(): void
     {
         $profileId1 = ProfileId::generate();
         $profileId2 = ProfileId::generate();
@@ -554,19 +557,14 @@ public function testAppend(): void
                 ])),
         ];
 
-        $this->store->append(
-            $messages,
-            new AppendCondition([], 0),
-        );
+        $this->store->append($messages);
 
         $stream = null;
 
         try {
-            $stream = $this->store->load(
-                new Criteria(
-                    new TagCriterion(['profile:' . $profileId1->toString()], ['test']),
-                ),
-            );
+            $stream = $this->store->query(new Query(
+                new QueryComponent(['profile:' . $profileId1->toString()]),
+            ));
 
             $messages = iterator_to_array($stream);
 
@@ -602,10 +600,7 @@ public function testAppendRaceCondition(): void
                 ->withHeader(new TagsHeader(['profile:' . $profileId2->toString()])),
         ];
 
-        $this->store->append(
-            $messages,
-            new AppendCondition([], 0),
-        );
+        $this->store->append($messages);
 
         $messages = [
             Message::create(new ExternEvent('test message'))
@@ -616,12 +611,12 @@ public function testAppendRaceCondition(): void
                 ])),
         ];
 
-        $this->expectException(UniqueConstraintViolation::class);
+        $this->expectException(AppendConditionNotMet::class);
 
         $this->store->append(
             $messages,
             new AppendCondition(
-                [['profile:' . $profileId1->toString()]],
+                new Query(new QueryComponent(['profile:' . $profileId1->toString()])),
                 0,
             ),
         );

From 213c6c529586734f485b5404aeaeca72fa0d1a2f Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Fri, 1 Aug 2025 13:33:36 +0200
Subject: [PATCH 08/22] refactor projection & query api

---
 src/DCB/CompositeProjection.php       | 52 ++++-----------------------
 src/DCB/Projection.php                |  6 ++++
 src/DCB/ProjectionBuilder.php         | 18 ++++++++++
 src/DCB/StoreDecisionModelBuilder.php | 10 +-----
 src/DCB/StoreProjectionBuilder.php    | 38 ++++++++++++++++++++
 src/Store/Query.php                   | 13 +++++++
 src/Store/QueryComponent.php          | 34 ++++++++++++++++++
 7 files changed, 116 insertions(+), 55 deletions(-)
 create mode 100644 src/DCB/ProjectionBuilder.php
 create mode 100644 src/DCB/StoreProjectionBuilder.php

diff --git a/src/DCB/CompositeProjection.php b/src/DCB/CompositeProjection.php
index 82e3c926..a6d14554 100644
--- a/src/DCB/CompositeProjection.php
+++ b/src/DCB/CompositeProjection.php
@@ -5,15 +5,9 @@
 namespace Patchlevel\EventSourcing\DCB;
 
 use Patchlevel\EventSourcing\Message\Message;
-use Patchlevel\EventSourcing\Store\Header\TagsHeader;
+use Patchlevel\EventSourcing\Store\Query;
 
-use function array_diff;
 use function array_map;
-use function array_merge;
-use function array_unique;
-use function array_values;
-use function in_array;
-use function sort;
 
 /**
  * @experimental
@@ -27,36 +21,15 @@ public function __construct(
     ) {
     }
 
-    /** @return list<string> */
-    public function tagFilter(): array
+    public function query(): Query
     {
-        $tags = [];
+        $query = new Query();
 
         foreach ($this->projections as $projection) {
-            $tags = array_merge($tags, $projection->tagFilter());
+            $query = $query->add($projection->queryComponent());
         }
 
-        return array_values(array_unique($tags));
-    }
-
-    /** @return list<list<string>> */
-    public function groupedTagFilter(): array
-    {
-        $result = [];
-
-        foreach ($this->projections as $projection) {
-            $tags = $projection->tagFilter();
-
-            sort($tags);
-
-            if (in_array($tags, $result, true)) {
-                continue;
-            }
-
-            $result[] = $tags;
-        }
-
-        return $result;
+        return $query;
     }
 
     /** @return array<string, mixed> */
@@ -69,12 +42,8 @@ public function initialState(): array
 
     public function apply(mixed $state, Message $message): mixed
     {
-        $tags = $message->header(TagsHeader::class)->tags;
-
         foreach ($this->projections as $name => $projection) {
-            $neededTags = $projection->tagFilter();
-
-            if (!$this->isSubset($neededTags, $tags)) {
+            if (!$projection->queryComponent()->match($message)) {
                 continue;
             }
 
@@ -83,13 +52,4 @@ public function apply(mixed $state, Message $message): mixed
 
         return $state;
     }
-
-    /**
-     * @param list<string> $needle
-     * @param list<string> $haystack
-     */
-    private function isSubset(array $needle, array $haystack): bool
-    {
-        return empty(array_diff($needle, $haystack));
-    }
 }
diff --git a/src/DCB/Projection.php b/src/DCB/Projection.php
index 099c4dc1..d1c6c507 100644
--- a/src/DCB/Projection.php
+++ b/src/DCB/Projection.php
@@ -7,6 +7,7 @@
 use Closure;
 use Patchlevel\EventSourcing\Attribute\Apply;
 use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Store\QueryComponent;
 use ReflectionClass;
 use RuntimeException;
 
@@ -26,6 +27,11 @@ abstract public function tagFilter(): array;
     /** @return S */
     abstract public function initialState(): mixed;
 
+    public function queryComponent(): QueryComponent
+    {
+        return new QueryComponent($this->tagFilter());
+    }
+
     /**
      * @param S $state
      *
diff --git a/src/DCB/ProjectionBuilder.php b/src/DCB/ProjectionBuilder.php
new file mode 100644
index 00000000..a67e72ad
--- /dev/null
+++ b/src/DCB/ProjectionBuilder.php
@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+/** @experimental */
+interface ProjectionBuilder
+{
+    /**
+     * @param array<string, Projection> $projections
+     *
+     * @return array<string, mixed>
+     */
+    public function build(
+        array $projections,
+    ): array;
+}
diff --git a/src/DCB/StoreDecisionModelBuilder.php b/src/DCB/StoreDecisionModelBuilder.php
index 49f824de..763d4f10 100644
--- a/src/DCB/StoreDecisionModelBuilder.php
+++ b/src/DCB/StoreDecisionModelBuilder.php
@@ -6,10 +6,6 @@
 
 use Patchlevel\EventSourcing\Store\AppendCondition;
 use Patchlevel\EventSourcing\Store\AppendStore;
-use Patchlevel\EventSourcing\Store\Query;
-use Patchlevel\EventSourcing\Store\QueryComponent;
-
-use function array_map;
 
 /** @experimental */
 final class StoreDecisionModelBuilder implements DecisionModelBuilder
@@ -25,11 +21,7 @@ public function build(
     ): DecisionModel {
         $projection = new CompositeProjection($projections);
 
-        $query = new Query(...array_map(
-            static fn (array $tags) => new QueryComponent($tags),
-            $projection->groupedTagFilter(),
-        ));
-
+        $query = $projection->query();
         $stream = $this->store->query($query);
 
         $state = $projection->initialState();
diff --git a/src/DCB/StoreProjectionBuilder.php b/src/DCB/StoreProjectionBuilder.php
new file mode 100644
index 00000000..53824e9f
--- /dev/null
+++ b/src/DCB/StoreProjectionBuilder.php
@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+use Patchlevel\EventSourcing\Store\AppendStore;
+
+/** @experimental */
+final class StoreProjectionBuilder implements ProjectionBuilder
+{
+    public function __construct(
+        private AppendStore $store,
+    ) {
+    }
+
+    /**
+     * @param array<string, Projection> $projections
+     *
+     * @return array<string, mixed>
+     */
+    public function build(
+        array $projections,
+    ): array {
+        $projection = new CompositeProjection($projections);
+
+        $query = $projection->query();
+        $stream = $this->store->query($query);
+
+        $state = $projection->initialState();
+
+        foreach ($stream as $message) {
+            $state = $projection->apply($state, $message);
+        }
+
+        return $state;
+    }
+}
diff --git a/src/Store/Query.php b/src/Store/Query.php
index 07ce1d68..3de4a9f0 100644
--- a/src/Store/Query.php
+++ b/src/Store/Query.php
@@ -14,4 +14,17 @@ public function __construct(
     ) {
         $this->components = $components;
     }
+
+    public function add(QueryComponent $component): self
+    {
+        foreach ($this->components as $c) {
+            if ($c->equals($component)) {
+                return $this;
+            }
+        }
+
+        $components = [...$this->components, $component];
+
+        return new self(...$components);
+    }
 }
diff --git a/src/Store/QueryComponent.php b/src/Store/QueryComponent.php
index b8713582..cf54c704 100644
--- a/src/Store/QueryComponent.php
+++ b/src/Store/QueryComponent.php
@@ -4,11 +4,45 @@
 
 namespace Patchlevel\EventSourcing\Store;
 
+use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Store\Header\TagsHeader;
+
+use function array_diff;
+use function sort;
+
 final class QueryComponent
 {
     /** @param list<string> $tags */
     public function __construct(
         public readonly array $tags,
     ) {
+        sort($tags);
+    }
+
+    public function match(Message $message): bool
+    {
+        if ($this->tags === []) {
+            return true;
+        }
+
+        if (!$message->hasHeader(TagsHeader::class)) {
+            return false;
+        }
+
+        return $this->isSubset($this->tags, $message->header(TagsHeader::class)->tags);
+    }
+
+    public function equals(self $queryComponent): bool
+    {
+        return $this->tags === $queryComponent->tags;
+    }
+
+    /**
+     * @param list<string> $needle
+     * @param list<string> $haystack
+     */
+    private function isSubset(array $needle, array $haystack): bool
+    {
+        return empty(array_diff($needle, $haystack));
     }
 }

From d4f47738be0bb1f6d96a95614f140cd44c5e63fb Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Fri, 1 Aug 2025 13:36:26 +0200
Subject: [PATCH 09/22] add missing experimental annotations

---
 src/Store/AppendConditionNotMet.php | 1 +
 src/Store/AppendStore.php           | 1 +
 src/Store/Query.php                 | 1 +
 src/Store/QueryComponent.php        | 1 +
 4 files changed, 4 insertions(+)

diff --git a/src/Store/AppendConditionNotMet.php b/src/Store/AppendConditionNotMet.php
index fd040264..f0ad8d61 100644
--- a/src/Store/AppendConditionNotMet.php
+++ b/src/Store/AppendConditionNotMet.php
@@ -4,6 +4,7 @@
 
 namespace Patchlevel\EventSourcing\Store;
 
+/** @experimental */
 class AppendConditionNotMet extends StoreException
 {
     public function __construct(
diff --git a/src/Store/AppendStore.php b/src/Store/AppendStore.php
index cfa31e53..479080e1 100644
--- a/src/Store/AppendStore.php
+++ b/src/Store/AppendStore.php
@@ -6,6 +6,7 @@
 
 use Patchlevel\EventSourcing\Message\Message;
 
+/** @experimental */
 interface AppendStore
 {
     /** @param iterable<Message> $messages */
diff --git a/src/Store/Query.php b/src/Store/Query.php
index 3de4a9f0..05664e9c 100644
--- a/src/Store/Query.php
+++ b/src/Store/Query.php
@@ -4,6 +4,7 @@
 
 namespace Patchlevel\EventSourcing\Store;
 
+/** @experimental */
 final class Query
 {
     /** @var list<QueryComponent> */
diff --git a/src/Store/QueryComponent.php b/src/Store/QueryComponent.php
index cf54c704..a96905b4 100644
--- a/src/Store/QueryComponent.php
+++ b/src/Store/QueryComponent.php
@@ -10,6 +10,7 @@
 use function array_diff;
 use function sort;
 
+/** @experimental */
 final class QueryComponent
 {
     /** @param list<string> $tags */

From 528e9cbf69f723871be0918e91d948085a18185f Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Sat, 9 Aug 2025 13:32:09 +0200
Subject: [PATCH 10/22] add Stringable Interface & refactor some code

---
 src/DCB/ApplyTrait.php                        | 166 ++++++++++++++++++
 src/DCB/AttributeEventTagExtractor.php        |   8 +-
 src/DCB/CompositeProjection.php               |   7 +-
 src/DCB/Projection.php                        |  72 +-------
 src/Metadata/PropertyType.php                 |  53 ++++++
 .../Normalizer/StringableNormalizer.php       |  79 +++++++++
 src/Store/Query.php                           |  18 +-
 .../{QueryComponent.php => SubQuery.php}      |   2 +-
 src/Store/TaggableDoctrineDbalStore.php       |   8 +-
 src/Stringable.php                            |  13 ++
 .../Course/CourseId.php                       |   4 +-
 .../Projection/CourseCapacityProjection.php   |   5 +-
 .../Course/Projection/CourseExists.php        |   8 +-
 .../NumberOfCourseSubscriptionsProjection.php |   5 +-
 ...NumberOfStudentSubscriptionsProjection.php |   5 +-
 .../StudentAlreadySubscribedProjection.php    |   5 +-
 .../Course/StudentId.php                      |   4 +-
 .../NextInvoiceNumberProjection.php           |   5 +-
 .../Store/TaggableDoctrineDbalStoreTest.php   |   6 +-
 19 files changed, 367 insertions(+), 106 deletions(-)
 create mode 100644 src/DCB/ApplyTrait.php
 create mode 100644 src/Metadata/PropertyType.php
 create mode 100644 src/Serializer/Normalizer/StringableNormalizer.php
 rename src/Store/{QueryComponent.php => SubQuery.php} (97%)
 create mode 100644 src/Stringable.php

diff --git a/src/DCB/ApplyTrait.php b/src/DCB/ApplyTrait.php
new file mode 100644
index 00000000..f6d6d66f
--- /dev/null
+++ b/src/DCB/ApplyTrait.php
@@ -0,0 +1,166 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Store\SubQuery;
+use ReflectionClass;
+use ReflectionIntersectionType;
+use ReflectionMethod;
+use ReflectionNamedType;
+use ReflectionUnionType;
+use function array_key_exists;
+use function array_keys;
+use function array_map;
+use function array_merge;
+use function class_exists;
+
+/**
+ * @experimental
+ */
+trait ApplyTrait
+{
+    /** @param array<class-string, string>|null $applyMethods */
+    private array|null $applyMethods = null;
+
+    public function apply(mixed $state, Message $message): mixed
+    {
+        if (!$this->subQuery()->match($message)) {
+            return $state;
+        }
+
+        $event = $message->event();
+        $applyMethods = $this->applyMethods();
+
+        if (array_key_exists($event::class, $applyMethods)) {
+            return $this->{$applyMethods[$event::class]}($state, $event);
+        }
+
+        return $state;
+    }
+
+    public function subQuery(): SubQuery
+    {
+        return new SubQuery(
+            $this->tagFilter(),
+            // $this->eventTypeFilter(),
+        );
+    }
+
+    public function eventTypeFilter(): array
+    {
+        return array_keys($this->applyMethods());
+    }
+
+    /** @return array<class-string, string> */
+    private function applyMethods(): array
+    {
+        if ($this->applyMethods !== null) {
+            return $this->applyMethods;
+        }
+
+        $reflector = new ReflectionClass($this);
+
+        $this->applyMethods = [];
+
+        foreach ($reflector->getMethods() as $method) {
+            $attributes = $method->getAttributes(Apply::class);
+
+            if ($attributes === []) {
+                continue;
+            }
+
+            $eventClasses = [];
+            $hasOneEmptyApply = false;
+            $hasOneNonEmptyApply = false;
+
+            foreach ($attributes as $attribute) {
+                $applyAttribute = $attribute->newInstance();
+                $eventClass = $applyAttribute->eventClass;
+
+                if ($eventClass !== null) {
+                    $hasOneNonEmptyApply = true;
+                    $eventClasses[] = $eventClass;
+
+                    continue;
+                }
+
+                if ($hasOneEmptyApply) {
+                    throw new DuplicateEmptyApplyAttribute($method->getName());
+                }
+
+                $hasOneEmptyApply = true;
+                $eventClasses = array_merge($eventClasses, $this->getEventClassesByPropertyTypes($method));
+            }
+
+            if ($hasOneEmptyApply && $hasOneNonEmptyApply) {
+                throw new MixedApplyAttributeUsage($method->getName());
+            }
+
+            foreach ($eventClasses as $eventClass) {
+                if (!class_exists($eventClass)) {
+                    throw new ArgumentTypeIsNotAClass($method->getName(), $eventClass);
+                }
+
+                if (array_key_exists($eventClass, $this->applyMethods)) {
+                    throw new DuplicateApplyMethod(
+                        $eventClass,
+                        $this->applyMethods[$eventClass],
+                        $method->getName(),
+                    );
+                }
+
+                $this->applyMethods[$eventClass] = $method->getName();
+            }
+        }
+
+        return $this->applyMethods;
+    }
+
+    /** @return array<string> */
+    private function getEventClassesByPropertyTypes(ReflectionMethod $method): array
+    {
+        $parameters = $method->getParameters();
+
+        if (array_key_exists(1, $parameters) === false) {
+            throw new ParameterIsMissing($method->getName(), 1);
+        }
+
+        $propertyType = $parameters[1]->getType();
+        $methodName = $method->getName();
+
+        if ($propertyType === null) {
+            throw new ArgumentTypeIsMissing($methodName);
+        }
+
+        if ($propertyType instanceof ReflectionIntersectionType) {
+            throw new ArgumentTypeIsMissing($methodName);
+        }
+
+        if ($propertyType instanceof ReflectionNamedType) {
+            return [$propertyType->getName()];
+        }
+
+        if ($propertyType instanceof ReflectionUnionType) {
+            return array_map(
+                static function (ReflectionNamedType|ReflectionIntersectionType $reflectionType) use ($methodName,
+                ): string {
+                    if ($reflectionType instanceof ReflectionIntersectionType) {
+                        throw new ArgumentTypeIsMissing($methodName);
+                    }
+
+                    return $reflectionType->getName();
+                },
+                $propertyType->getTypes(),
+            );
+        }
+
+        return [];
+    }
+
+    /** @return list<string> */
+    public abstract function tagFilter(): array;
+}
diff --git a/src/DCB/AttributeEventTagExtractor.php b/src/DCB/AttributeEventTagExtractor.php
index 4b54c063..566c3010 100644
--- a/src/DCB/AttributeEventTagExtractor.php
+++ b/src/DCB/AttributeEventTagExtractor.php
@@ -4,11 +4,11 @@
 
 namespace Patchlevel\EventSourcing\DCB;
 
-use Patchlevel\EventSourcing\Aggregate\AggregateRootId;
 use Patchlevel\EventSourcing\Attribute\EventTag;
+use Patchlevel\EventSourcing\Stringable;
 use ReflectionClass;
 use RuntimeException;
-use Stringable;
+use Stringable as NativeStringable;
 
 use function array_keys;
 use function get_debug_type;
@@ -39,11 +39,11 @@ public function extract(object $event): array
 
             $value = $property->getValue($event);
 
-            if ($value instanceof AggregateRootId) {
+            if ($value instanceof Stringable) {
                 $value = $value->toString();
             }
 
-            if ($value instanceof Stringable || is_int($value)) {
+            if ($value instanceof NativeStringable || is_int($value)) {
                 $value = (string)$value;
             }
 
diff --git a/src/DCB/CompositeProjection.php b/src/DCB/CompositeProjection.php
index a6d14554..5742fe65 100644
--- a/src/DCB/CompositeProjection.php
+++ b/src/DCB/CompositeProjection.php
@@ -6,7 +6,6 @@
 
 use Patchlevel\EventSourcing\Message\Message;
 use Patchlevel\EventSourcing\Store\Query;
-
 use function array_map;
 
 /**
@@ -26,7 +25,7 @@ public function query(): Query
         $query = new Query();
 
         foreach ($this->projections as $projection) {
-            $query = $query->add($projection->queryComponent());
+            $query = $query->add($projection->subQuery());
         }
 
         return $query;
@@ -43,10 +42,6 @@ public function initialState(): array
     public function apply(mixed $state, Message $message): mixed
     {
         foreach ($this->projections as $name => $projection) {
-            if (!$projection->queryComponent()->match($message)) {
-                continue;
-            }
-
             $state[$name] = $projection->apply($state[$name], $message);
         }
 
diff --git a/src/DCB/Projection.php b/src/DCB/Projection.php
index d1c6c507..f519c6cd 100644
--- a/src/DCB/Projection.php
+++ b/src/DCB/Projection.php
@@ -4,86 +4,24 @@
 
 namespace Patchlevel\EventSourcing\DCB;
 
-use Closure;
-use Patchlevel\EventSourcing\Attribute\Apply;
 use Patchlevel\EventSourcing\Message\Message;
-use Patchlevel\EventSourcing\Store\QueryComponent;
-use ReflectionClass;
-use RuntimeException;
-
-use function is_a;
-use function method_exists;
-use function sprintf;
+use Patchlevel\EventSourcing\Store\SubQuery;
 
 /**
  * @experimental
  * @template S as mixed
  */
-abstract class Projection
+interface Projection
 {
-    /** @return list<string> */
-    abstract public function tagFilter(): array;
-
     /** @return S */
-    abstract public function initialState(): mixed;
-
-    public function queryComponent(): QueryComponent
-    {
-        return new QueryComponent($this->tagFilter());
-    }
+    public function initialState(): mixed;
 
     /**
      * @param S $state
      *
      * @return S
      */
-    public function apply(mixed $state, Message $message): mixed
-    {
-        $event = $message->event();
-
-        $method = 'apply' . (new ReflectionClass($event))->getShortName();
-
-        if (method_exists($this, $method)) {
-            $state = $this->{$method}($state, $event);
-        }
-
-        return $state;
-    }
-
-    /** @return array<class-string, Closure(mixed, object): mixed> */
-    private static function applies(): array
-    {
-        $reflection = new ReflectionClass(static::class);
-        $methods = $reflection->getMethods();
-
-        $applies = [];
-
-        foreach ($methods as $method) {
-            $attributes = $method->getAttributes(Apply::class);
-
-            if ($attributes === []) {
-                continue;
-            }
-
-            foreach ($attributes as $attribute) {
-                /** @var Apply $apply */
-                $apply = $attribute->newInstance();
-
-                if ($apply->class === null) {
-                    $applies[$method->getName()] = Closure::fromCallable([$reflection->getName(), $method->getName()]);
-                    continue;
-                }
-
-                if (!is_a($apply->class, static::class, true)) {
-                    throw new RuntimeException(
-                        sprintf('Apply class %s must be a subclass of %s', $apply->class, static::class),
-                    );
-                }
-
-                $applies[$apply->class] = Closure::fromCallable([$reflection->getName(), $method->getName()]);
-            }
-        }
+    public function apply(mixed $state, Message $message): mixed;
 
-        return $applies;
-    }
+    public function subQuery(): SubQuery;
 }
diff --git a/src/Metadata/PropertyType.php b/src/Metadata/PropertyType.php
new file mode 100644
index 00000000..fbfda150
--- /dev/null
+++ b/src/Metadata/PropertyType.php
@@ -0,0 +1,53 @@
+<?php
+
+namespace Patchlevel\EventSourcing\Metadata;
+
+use ReflectionParameter;
+use Symfony\Component\TypeInfo\Type;
+use Symfony\Component\TypeInfo\Type\ObjectType;
+use Symfony\Component\TypeInfo\Type\UnionType;
+use Symfony\Component\TypeInfo\TypeResolver\TypeResolver;
+
+class PropertyType
+{
+    private TypeResolver $typeResolver;
+
+    public function __construct()
+    {
+        $this->typeResolver = TypeResolver::create();
+    }
+
+    /**
+     * @param class-string $class
+     * @return array<string>
+     */
+    public function getEventClassesByPropertyTypes(ReflectionParameter $parameter): array
+    {
+        $propertyType = $parameter->getType();
+
+        if ($propertyType === null) {
+            throw new ArgumentTypeIsMissing($methodName);
+        }
+
+        $type = $this->typeResolver->resolve($propertyType);
+
+        if ($type instanceof ObjectType) {
+            return [$type->getClassName()];
+        }
+
+        if ($type instanceof UnionType) {
+            return array_map(
+                static function (Type $type): string {
+                    if ($type instanceof ObjectType) {
+                        return $type->getClassName();
+                    }
+
+                    throw new ArgumentTypeIsMissing($methodName);
+                },
+                $type->getTypes(),
+            );
+        }
+
+        throw new ArgumentTypeIsMissing($methodName);
+    }
+}
\ No newline at end of file
diff --git a/src/Serializer/Normalizer/StringableNormalizer.php b/src/Serializer/Normalizer/StringableNormalizer.php
new file mode 100644
index 00000000..a7314882
--- /dev/null
+++ b/src/Serializer/Normalizer/StringableNormalizer.php
@@ -0,0 +1,79 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Serializer\Normalizer;
+
+use Attribute;
+use Patchlevel\EventSourcing\Stringable;
+use Patchlevel\Hydrator\Normalizer\InvalidArgument;
+use Patchlevel\Hydrator\Normalizer\InvalidType;
+use Patchlevel\Hydrator\Normalizer\Normalizer;
+use Patchlevel\Hydrator\Normalizer\TypeAwareNormalizer;
+use Symfony\Component\TypeInfo\Type;
+
+use Symfony\Component\TypeInfo\Type\ObjectType;
+use function is_string;
+
+#[Attribute(Attribute::TARGET_PROPERTY | Attribute::TARGET_CLASS)]
+final class StringableNormalizer implements Normalizer, TypeAwareNormalizer
+{
+    public function __construct(
+        /** @var class-string<Stringable>|null */
+        private string|null $stringableClass = null,
+    ) {
+    }
+
+    public function normalize(mixed $value): string|null
+    {
+        if ($value === null) {
+            return null;
+        }
+
+        $class = $this->stringableClass();
+
+        if (!$value instanceof Stringable) {
+            throw InvalidArgument::withWrongType($class, $value);
+        }
+
+        return $value->toString();
+    }
+
+    public function denormalize(mixed $value): Stringable|null
+    {
+        if ($value === null) {
+            return null;
+        }
+
+        if (!is_string($value)) {
+            throw InvalidArgument::withWrongType('string', $value);
+        }
+
+        $class = $this->stringableClass();
+
+        return $class::fromString($value);
+    }
+
+    /** @return class-string<Stringable> */
+    public function stringableClass(): string
+    {
+        if ($this->stringableClass === null) {
+            throw InvalidType::missingType();
+        }
+
+        return $this->stringableClass;
+    }
+
+    public function handleType(Type|null $type): void
+    {
+        if ($type === null || $this->stringableClass !== null) {
+            return;
+        }
+
+        if (!$type instanceof ObjectType) {
+            return;
+        }
+
+        $this->stringableClass = $type->getClassName();
+    }
+}
diff --git a/src/Store/Query.php b/src/Store/Query.php
index 05664e9c..9099eccb 100644
--- a/src/Store/Query.php
+++ b/src/Store/Query.php
@@ -7,25 +7,23 @@
 /** @experimental */
 final class Query
 {
-    /** @var list<QueryComponent> */
-    public readonly array $components;
+    /** @var list<SubQuery> */
+    public readonly array $subQueries;
 
     public function __construct(
-        QueryComponent ...$components,
+        SubQuery ...$subQueries,
     ) {
-        $this->components = $components;
+        $this->subQueries = $subQueries;
     }
 
-    public function add(QueryComponent $component): self
+    public function add(SubQuery $subQuery): self
     {
-        foreach ($this->components as $c) {
-            if ($c->equals($component)) {
+        foreach ($this->subQueries as $query) {
+            if ($query->equals($subQuery)) {
                 return $this;
             }
         }
 
-        $components = [...$this->components, $component];
-
-        return new self(...$components);
+        return new self($subQuery, ...$this->subQueries);
     }
 }
diff --git a/src/Store/QueryComponent.php b/src/Store/SubQuery.php
similarity index 97%
rename from src/Store/QueryComponent.php
rename to src/Store/SubQuery.php
index a96905b4..4e95d248 100644
--- a/src/Store/QueryComponent.php
+++ b/src/Store/SubQuery.php
@@ -11,7 +11,7 @@
 use function sort;
 
 /** @experimental */
-final class QueryComponent
+final class SubQuery
 {
     /** @param list<string> $tags */
     public function __construct(
diff --git a/src/Store/TaggableDoctrineDbalStore.php b/src/Store/TaggableDoctrineDbalStore.php
index bd44c3b0..d3fd7e86 100644
--- a/src/Store/TaggableDoctrineDbalStore.php
+++ b/src/Store/TaggableDoctrineDbalStore.php
@@ -449,7 +449,7 @@ public function append(iterable $messages, AppendCondition|null $appendCondition
                 implode(' UNION ALL ', $selects),
             );
 
-            if ($appendCondition instanceof AppendCondition && $appendCondition->query->components !== []) {
+            if ($appendCondition instanceof AppendCondition && $appendCondition->query->subQueries !== []) {
                 $queryBuilder = $this->connection->createQueryBuilder()
                     ->select('events.id')
                     ->from($this->config['table_name'], 'events')
@@ -807,7 +807,7 @@ private function uniqueParameterGenerator(): Closure
 
     private function queryCondition(QueryBuilder $builder, Query $query): void
     {
-        if ($query->components === []) {
+        if ($query->subQueries === []) {
             return;
         }
 
@@ -815,7 +815,7 @@ private function queryCondition(QueryBuilder $builder, Query $query): void
 
         $uniqueParameterGenerator = $this->uniqueParameterGenerator();
 
-        foreach ($query->components as $component) {
+        foreach ($query->subQueries as $subQuery) {
             $subQueryBuilder = $this->connection->createQueryBuilder()
                 ->select('id')
                 ->from($this->config['table_name']);
@@ -832,7 +832,7 @@ private function queryCondition(QueryBuilder $builder, Query $query): void
                 throw new RuntimeException('x');
             }
 
-            $builder->setParameter($parameterName, json_encode($component->tags));
+            $builder->setParameter($parameterName, json_encode($subQuery->tags));
 
             $subqueries[] = $subQueryBuilder->getSQL();
         }
diff --git a/src/Stringable.php b/src/Stringable.php
new file mode 100644
index 00000000..ff4abdaf
--- /dev/null
+++ b/src/Stringable.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace Patchlevel\EventSourcing;
+
+use Patchlevel\EventSourcing\Serializer\Normalizer\StringableNormalizer;
+
+#[StringableNormalizer]
+interface Stringable
+{
+    public function toString(): string;
+
+    public static function fromString(string $value): self;
+}
\ No newline at end of file
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/CourseId.php b/tests/Integration/DynamicConsistencyBoundary/Course/CourseId.php
index 26cedff3..6a9fb704 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/CourseId.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/CourseId.php
@@ -4,10 +4,10 @@
 
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course;
 
-use Patchlevel\EventSourcing\Aggregate\AggregateRootId;
 use Patchlevel\EventSourcing\Aggregate\RamseyUuidV7Behaviour;
+use Patchlevel\EventSourcing\Stringable;
 
-final class CourseId implements AggregateRootId
+final class CourseId implements Stringable
 {
     use RamseyUuidV7Behaviour;
 }
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php
index d76f62a9..b3680e22 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php
@@ -5,13 +5,16 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\ApplyTrait;
 use Patchlevel\EventSourcing\DCB\Projection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseCapacityChanged;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseDefined;
 
-final class CourseCapacityProjection extends Projection
+final class CourseCapacityProjection implements Projection
 {
+    use ApplyTrait;
+
     public function __construct(
         private readonly CourseId $courseId,
     ) {
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php
index 4854525e..43372573 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php
@@ -5,13 +5,17 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\ApplyTrait;
 use Patchlevel\EventSourcing\DCB\Projection;
+use Patchlevel\EventSourcing\Store\SubQuery;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseDefined;
 
-/** @extends Projection<bool> */
-final class CourseExists extends Projection
+/** @implements Projection<bool> */
+final class CourseExists implements Projection
 {
+    use ApplyTrait;
+
     public function __construct(
         private readonly CourseId $courseId,
     ) {
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php
index 5b37cab1..01655362 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php
@@ -5,12 +5,15 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\ApplyTrait;
 use Patchlevel\EventSourcing\DCB\Projection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\StudentSubscribedToCourse;
 
-final class NumberOfCourseSubscriptionsProjection extends Projection
+final class NumberOfCourseSubscriptionsProjection implements Projection
 {
+    use ApplyTrait;
+
     public function __construct(
         private readonly CourseId $courseId,
     ) {
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php
index 79011691..87a214d6 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php
@@ -5,12 +5,15 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\ApplyTrait;
 use Patchlevel\EventSourcing\DCB\Projection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\StudentSubscribedToCourse;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\StudentId;
 
-final class NumberOfStudentSubscriptionsProjection extends Projection
+final class NumberOfStudentSubscriptionsProjection implements Projection
 {
+    use ApplyTrait;
+
     public function __construct(
         private readonly StudentId $studentId,
     ) {
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php
index 6f652d46..887748c8 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php
@@ -5,13 +5,16 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\ApplyTrait;
 use Patchlevel\EventSourcing\DCB\Projection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\StudentSubscribedToCourse;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\StudentId;
 
-final class StudentAlreadySubscribedProjection extends Projection
+final class StudentAlreadySubscribedProjection implements Projection
 {
+    use ApplyTrait;
+
     public function __construct(
         private readonly StudentId $studentId,
         private readonly CourseId $courseId,
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/StudentId.php b/tests/Integration/DynamicConsistencyBoundary/Course/StudentId.php
index 62d11f76..49b5209e 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/StudentId.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/StudentId.php
@@ -4,10 +4,10 @@
 
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course;
 
-use Patchlevel\EventSourcing\Aggregate\AggregateRootId;
 use Patchlevel\EventSourcing\Aggregate\RamseyUuidV7Behaviour;
+use Patchlevel\EventSourcing\Stringable;
 
-final class StudentId implements AggregateRootId
+final class StudentId implements Stringable
 {
     use RamseyUuidV7Behaviour;
 }
diff --git a/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php b/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
index 6b6d3914..6f9ee822 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
@@ -4,11 +4,14 @@
 
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Projection;
 
+use Patchlevel\EventSourcing\DCB\ApplyTrait;
 use Patchlevel\EventSourcing\DCB\Projection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Event\InvoiceCreated;
 
-final class NextInvoiceNumberProjection extends Projection
+final class NextInvoiceNumberProjection implements Projection
 {
+    use ApplyTrait;
+
     /** @return list<string> */
     public function tagFilter(): array
     {
diff --git a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
index 1cd7c6fe..58bac97c 100644
--- a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
+++ b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
@@ -23,7 +23,7 @@
 use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
 use Patchlevel\EventSourcing\Store\Header\TagsHeader;
 use Patchlevel\EventSourcing\Store\Query;
-use Patchlevel\EventSourcing\Store\QueryComponent;
+use Patchlevel\EventSourcing\Store\SubQuery;
 use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
 use Patchlevel\EventSourcing\Store\UniqueConstraintViolation;
 use Patchlevel\EventSourcing\Tests\DbalManager;
@@ -563,7 +563,7 @@ public function testAppendAndQuery(): void
 
         try {
             $stream = $this->store->query(new Query(
-                new QueryComponent(['profile:' . $profileId1->toString()]),
+                new SubQuery(['profile:' . $profileId1->toString()]),
             ));
 
             $messages = iterator_to_array($stream);
@@ -616,7 +616,7 @@ public function testAppendRaceCondition(): void
         $this->store->append(
             $messages,
             new AppendCondition(
-                new Query(new QueryComponent(['profile:' . $profileId1->toString()])),
+                new Query(new SubQuery(['profile:' . $profileId1->toString()])),
                 0,
             ),
         );

From dd07a3f94102e9df06defcfe14d15d8e846238cf Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Tue, 12 Aug 2025 12:57:53 +0200
Subject: [PATCH 11/22] add event type filter

---
 src/DCB/CompositeProjection.php               |   1 +
 src/DCB/{ApplyTrait.php => EventRouter.php}   |  12 +-
 src/Metadata/PropertyType.php                 |   7 +-
 .../Normalizer/StringableNormalizer.php       |   2 +-
 src/Store/SubQuery.php                        |  19 +-
 src/Store/TaggableDoctrineDbalStore.php       |  50 +++-
 src/Stringable.php                            |   4 +-
 .../Projection/CourseCapacityProjection.php   |   4 +-
 .../Course/Projection/CourseExists.php        |   5 +-
 .../NumberOfCourseSubscriptionsProjection.php |   4 +-
 ...NumberOfStudentSubscriptionsProjection.php |   4 +-
 .../StudentAlreadySubscribedProjection.php    |   4 +-
 .../DynamicConsistencyBoundaryTest.php        |   6 +-
 .../NextInvoiceNumberProjection.php           |   4 +-
 .../Store/TaggableDoctrineDbalStoreTest.php   | 247 ++++++++++++++++--
 15 files changed, 314 insertions(+), 59 deletions(-)
 rename src/DCB/{ApplyTrait.php => EventRouter.php} (96%)

diff --git a/src/DCB/CompositeProjection.php b/src/DCB/CompositeProjection.php
index 5742fe65..1880a6f4 100644
--- a/src/DCB/CompositeProjection.php
+++ b/src/DCB/CompositeProjection.php
@@ -6,6 +6,7 @@
 
 use Patchlevel\EventSourcing\Message\Message;
 use Patchlevel\EventSourcing\Store\Query;
+
 use function array_map;
 
 /**
diff --git a/src/DCB/ApplyTrait.php b/src/DCB/EventRouter.php
similarity index 96%
rename from src/DCB/ApplyTrait.php
rename to src/DCB/EventRouter.php
index f6d6d66f..2483fa83 100644
--- a/src/DCB/ApplyTrait.php
+++ b/src/DCB/EventRouter.php
@@ -12,16 +12,15 @@
 use ReflectionMethod;
 use ReflectionNamedType;
 use ReflectionUnionType;
+
 use function array_key_exists;
 use function array_keys;
 use function array_map;
 use function array_merge;
 use function class_exists;
 
-/**
- * @experimental
- */
-trait ApplyTrait
+/** @experimental */
+trait EventRouter
 {
     /** @param array<class-string, string>|null $applyMethods */
     private array|null $applyMethods = null;
@@ -46,10 +45,11 @@ public function subQuery(): SubQuery
     {
         return new SubQuery(
             $this->tagFilter(),
-            // $this->eventTypeFilter(),
+            $this->eventTypeFilter(),
         );
     }
 
+    /** @return list<class-string> */
     public function eventTypeFilter(): array
     {
         return array_keys($this->applyMethods());
@@ -162,5 +162,5 @@ static function (ReflectionNamedType|ReflectionIntersectionType $reflectionType)
     }
 
     /** @return list<string> */
-    public abstract function tagFilter(): array;
+    abstract public function tagFilter(): array;
 }
diff --git a/src/Metadata/PropertyType.php b/src/Metadata/PropertyType.php
index fbfda150..ccbf5513 100644
--- a/src/Metadata/PropertyType.php
+++ b/src/Metadata/PropertyType.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Patchlevel\EventSourcing\Metadata;
 
 use ReflectionParameter;
@@ -8,6 +10,8 @@
 use Symfony\Component\TypeInfo\Type\UnionType;
 use Symfony\Component\TypeInfo\TypeResolver\TypeResolver;
 
+use function array_map;
+
 class PropertyType
 {
     private TypeResolver $typeResolver;
@@ -19,6 +23,7 @@ public function __construct()
 
     /**
      * @param class-string $class
+     *
      * @return array<string>
      */
     public function getEventClassesByPropertyTypes(ReflectionParameter $parameter): array
@@ -50,4 +55,4 @@ static function (Type $type): string {
 
         throw new ArgumentTypeIsMissing($methodName);
     }
-}
\ No newline at end of file
+}
diff --git a/src/Serializer/Normalizer/StringableNormalizer.php b/src/Serializer/Normalizer/StringableNormalizer.php
index a7314882..13c51854 100644
--- a/src/Serializer/Normalizer/StringableNormalizer.php
+++ b/src/Serializer/Normalizer/StringableNormalizer.php
@@ -11,8 +11,8 @@
 use Patchlevel\Hydrator\Normalizer\Normalizer;
 use Patchlevel\Hydrator\Normalizer\TypeAwareNormalizer;
 use Symfony\Component\TypeInfo\Type;
-
 use Symfony\Component\TypeInfo\Type\ObjectType;
+
 use function is_string;
 
 #[Attribute(Attribute::TARGET_PROPERTY | Attribute::TARGET_CLASS)]
diff --git a/src/Store/SubQuery.php b/src/Store/SubQuery.php
index 4e95d248..2bd3e1fd 100644
--- a/src/Store/SubQuery.php
+++ b/src/Store/SubQuery.php
@@ -8,21 +8,27 @@
 use Patchlevel\EventSourcing\Store\Header\TagsHeader;
 
 use function array_diff;
+use function in_array;
 use function sort;
 
 /** @experimental */
 final class SubQuery
 {
-    /** @param list<string> $tags */
+    /**
+     * @param list<string>       $tags
+     * @param list<class-string> $events
+     */
     public function __construct(
-        public readonly array $tags,
+        public readonly array $tags = [],
+        public readonly array $events = [],
     ) {
         sort($tags);
+        sort($events);
     }
 
     public function match(Message $message): bool
     {
-        if ($this->tags === []) {
+        if ($this->tags === [] && $this->events === []) {
             return true;
         }
 
@@ -30,12 +36,17 @@ public function match(Message $message): bool
             return false;
         }
 
+        if ($this->events !== [] && !in_array($message->event()::class, $this->events, true)) {
+            return false;
+        }
+
         return $this->isSubset($this->tags, $message->header(TagsHeader::class)->tags);
     }
 
     public function equals(self $queryComponent): bool
     {
-        return $this->tags === $queryComponent->tags;
+        return $this->tags === $queryComponent->tags
+            && $this->events === $queryComponent->events;
     }
 
     /**
diff --git a/src/Store/TaggableDoctrineDbalStore.php b/src/Store/TaggableDoctrineDbalStore.php
index d3fd7e86..f2dde8ea 100644
--- a/src/Store/TaggableDoctrineDbalStore.php
+++ b/src/Store/TaggableDoctrineDbalStore.php
@@ -23,6 +23,7 @@
 use Patchlevel\EventSourcing\Message\Message;
 use Patchlevel\EventSourcing\Message\Serializer\DefaultHeadersSerializer;
 use Patchlevel\EventSourcing\Message\Serializer\HeadersSerializer;
+use Patchlevel\EventSourcing\Metadata\Event\EventRegistry;
 use Patchlevel\EventSourcing\Schema\DoctrineSchemaConfigurator;
 use Patchlevel\EventSourcing\Serializer\EventSerializer;
 use Patchlevel\EventSourcing\Store\Criteria\ArchivedCriterion;
@@ -48,6 +49,7 @@
 
 use function array_fill;
 use function array_filter;
+use function array_map;
 use function array_merge;
 use function array_values;
 use function class_exists;
@@ -97,6 +99,7 @@ final class TaggableDoctrineDbalStore implements StreamStore, AppendStore, Subsc
     public function __construct(
         private readonly Connection $connection,
         private readonly EventSerializer $eventSerializer,
+        private readonly EventRegistry $eventRegistry,
         HeadersSerializer|null $headersSerializer = null,
         ClockInterface|null $clock = null,
         array $config = [],
@@ -449,7 +452,7 @@ public function append(iterable $messages, AppendCondition|null $appendCondition
                 implode(' UNION ALL ', $selects),
             );
 
-            if ($appendCondition instanceof AppendCondition && $appendCondition->query->subQueries !== []) {
+            if ($appendCondition instanceof AppendCondition) {
                 $queryBuilder = $this->connection->createQueryBuilder()
                     ->select('events.id')
                     ->from($this->config['table_name'], 'events')
@@ -816,27 +819,52 @@ private function queryCondition(QueryBuilder $builder, Query $query): void
         $uniqueParameterGenerator = $this->uniqueParameterGenerator();
 
         foreach ($query->subQueries as $subQuery) {
+            if ($subQuery->tags === [] && $subQuery->events === []) {
+                continue;
+            }
+
             $subQueryBuilder = $this->connection->createQueryBuilder()
                 ->select('id')
                 ->from($this->config['table_name']);
 
-            $parameterName = $uniqueParameterGenerator();
+            if ($subQuery->tags !== []) {
+                $tagParameterName = $uniqueParameterGenerator();
 
-            if ($this->isSQLite) {
-                $subQueryBuilder->andWhere("NOT EXISTS(SELECT value FROM JSON_EACH(:{$parameterName}) WHERE value NOT IN (SELECT value FROM JSON_EACH(tags)))");
-            } elseif ($this->isPostgres) {
-                $subQueryBuilder->andWhere("tags @> :{$parameterName}::jsonb");
-            } elseif ($this->isMysql || $this->isMariaDb) {
-                $subQueryBuilder->andWhere("JSON_CONTAINS(tags, :{$parameterName})");
-            } else {
-                throw new RuntimeException('x');
+                if ($this->isSQLite) {
+                    $subQueryBuilder->andWhere("NOT EXISTS(SELECT value FROM JSON_EACH(:{$tagParameterName}) WHERE value NOT IN (SELECT value FROM JSON_EACH(tags)))");
+                } elseif ($this->isPostgres) {
+                    $subQueryBuilder->andWhere("tags @> :{$tagParameterName}::jsonb");
+                } elseif ($this->isMysql || $this->isMariaDb) {
+                    $subQueryBuilder->andWhere("JSON_CONTAINS(tags, :{$tagParameterName})");
+                } else {
+                    throw new RuntimeException('x');
+                }
+
+                $builder->setParameter($tagParameterName, json_encode($subQuery->tags));
             }
 
-            $builder->setParameter($parameterName, json_encode($subQuery->tags));
+            if ($subQuery->events !== []) {
+                $eventParameterName = $uniqueParameterGenerator();
+
+                $subQueryBuilder->andWhere("event_name IN (:{$eventParameterName})");
+
+                $builder->setParameter(
+                    $eventParameterName,
+                    array_map(
+                        fn (string $event) => $this->eventRegistry->eventName($event),
+                        $subQuery->events,
+                    ),
+                    ArrayParameterType::STRING,
+                );
+            }
 
             $subqueries[] = $subQueryBuilder->getSQL();
         }
 
+        if ($subqueries === []) {
+            return;
+        }
+
         $joinQueryBuilder = $this->connection->createQueryBuilder()
             ->select('id')
             ->from('(' . implode(' UNION ALL ', $subqueries) . ')', 'j')
diff --git a/src/Stringable.php b/src/Stringable.php
index ff4abdaf..ec6e4679 100644
--- a/src/Stringable.php
+++ b/src/Stringable.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Patchlevel\EventSourcing;
 
 use Patchlevel\EventSourcing\Serializer\Normalizer\StringableNormalizer;
@@ -10,4 +12,4 @@ interface Stringable
     public function toString(): string;
 
     public static function fromString(string $value): self;
-}
\ No newline at end of file
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php
index b3680e22..b7644667 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php
@@ -5,7 +5,7 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\ApplyTrait;
+use Patchlevel\EventSourcing\DCB\EventRouter;
 use Patchlevel\EventSourcing\DCB\Projection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseCapacityChanged;
@@ -13,7 +13,7 @@
 
 final class CourseCapacityProjection implements Projection
 {
-    use ApplyTrait;
+    use EventRouter;
 
     public function __construct(
         private readonly CourseId $courseId,
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php
index 43372573..7523df05 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php
@@ -5,16 +5,15 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\ApplyTrait;
+use Patchlevel\EventSourcing\DCB\EventRouter;
 use Patchlevel\EventSourcing\DCB\Projection;
-use Patchlevel\EventSourcing\Store\SubQuery;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseDefined;
 
 /** @implements Projection<bool> */
 final class CourseExists implements Projection
 {
-    use ApplyTrait;
+    use EventRouter;
 
     public function __construct(
         private readonly CourseId $courseId,
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php
index 01655362..88c48c82 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php
@@ -5,14 +5,14 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\ApplyTrait;
+use Patchlevel\EventSourcing\DCB\EventRouter;
 use Patchlevel\EventSourcing\DCB\Projection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\StudentSubscribedToCourse;
 
 final class NumberOfCourseSubscriptionsProjection implements Projection
 {
-    use ApplyTrait;
+    use EventRouter;
 
     public function __construct(
         private readonly CourseId $courseId,
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php
index 87a214d6..a3045d09 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php
@@ -5,14 +5,14 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\ApplyTrait;
+use Patchlevel\EventSourcing\DCB\EventRouter;
 use Patchlevel\EventSourcing\DCB\Projection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\StudentSubscribedToCourse;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\StudentId;
 
 final class NumberOfStudentSubscriptionsProjection implements Projection
 {
-    use ApplyTrait;
+    use EventRouter;
 
     public function __construct(
         private readonly StudentId $studentId,
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php
index 887748c8..83673d00 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php
@@ -5,7 +5,7 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\ApplyTrait;
+use Patchlevel\EventSourcing\DCB\EventRouter;
 use Patchlevel\EventSourcing\DCB\Projection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\StudentSubscribedToCourse;
@@ -13,7 +13,7 @@
 
 final class StudentAlreadySubscribedProjection implements Projection
 {
-    use ApplyTrait;
+    use EventRouter;
 
     public function __construct(
         private readonly StudentId $studentId,
diff --git a/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php b/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php
index 2e1820ce..608d8af5 100644
--- a/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php
+++ b/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php
@@ -9,7 +9,7 @@
 use Patchlevel\EventSourcing\CommandBus\SyncCommandBus;
 use Patchlevel\EventSourcing\DCB\StoreDecisionModelBuilder;
 use Patchlevel\EventSourcing\DCB\StoreEventAppender;
-use Patchlevel\EventSourcing\Message\Serializer\DefaultHeadersSerializer;
+use Patchlevel\EventSourcing\Metadata\Event\AttributeEventRegistryFactory;
 use Patchlevel\EventSourcing\Schema\DoctrineSchemaDirector;
 use Patchlevel\EventSourcing\Serializer\DefaultEventSerializer;
 use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
@@ -47,7 +47,7 @@ public function testCourse(): void
         $store = new TaggableDoctrineDbalStore(
             $this->connection,
             DefaultEventSerializer::createFromPaths([__DIR__ . '/Course/Event']),
-            DefaultHeadersSerializer::createDefault(),
+            (new AttributeEventRegistryFactory())->create([__DIR__ . '/Course/Event']),
         );
 
         $decisionModelBuilder = new StoreDecisionModelBuilder($store);
@@ -85,7 +85,7 @@ public function testInvoice(): void
         $store = new TaggableDoctrineDbalStore(
             $this->connection,
             DefaultEventSerializer::createFromPaths([__DIR__ . '/Invoice/Event']),
-            DefaultHeadersSerializer::createDefault(),
+            (new AttributeEventRegistryFactory())->create([__DIR__ . '/Invoice/Event']),
         );
 
         $decisionModelBuilder = new StoreDecisionModelBuilder($store);
diff --git a/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php b/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
index 6f9ee822..b474a916 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
@@ -4,13 +4,13 @@
 
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Projection;
 
-use Patchlevel\EventSourcing\DCB\ApplyTrait;
+use Patchlevel\EventSourcing\DCB\EventRouter;
 use Patchlevel\EventSourcing\DCB\Projection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Event\InvoiceCreated;
 
 final class NextInvoiceNumberProjection implements Projection
 {
-    use ApplyTrait;
+    use EventRouter;
 
     /** @return list<string> */
     public function tagFilter(): array
diff --git a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
index 58bac97c..094ecede 100644
--- a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
+++ b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
@@ -8,6 +8,7 @@
 use Doctrine\DBAL\Connection;
 use Patchlevel\EventSourcing\Clock\FrozenClock;
 use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Metadata\Event\AttributeEventRegistryFactory;
 use Patchlevel\EventSourcing\Schema\DoctrineSchemaDirector;
 use Patchlevel\EventSourcing\Serializer\DefaultEventSerializer;
 use Patchlevel\EventSourcing\Store\AppendCondition;
@@ -23,6 +24,7 @@
 use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
 use Patchlevel\EventSourcing\Store\Header\TagsHeader;
 use Patchlevel\EventSourcing\Store\Query;
+use Patchlevel\EventSourcing\Store\Stream;
 use Patchlevel\EventSourcing\Store\SubQuery;
 use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
 use Patchlevel\EventSourcing\Store\UniqueConstraintViolation;
@@ -32,7 +34,9 @@
 use PHPUnit\Framework\Attributes\CoversNothing;
 use PHPUnit\Framework\TestCase;
 use Psr\Clock\ClockInterface;
+use RuntimeException;
 
+use function count;
 use function iterator_to_array;
 use function json_decode;
 use function sprintf;
@@ -54,6 +58,7 @@ public function setUp(): void
         $this->store = new TaggableDoctrineDbalStore(
             $this->connection,
             DefaultEventSerializer::createFromPaths([__DIR__ . '/Events']),
+            (new AttributeEventRegistryFactory())->create([__DIR__ . '/Events']),
             clock: $this->clock,
         );
 
@@ -135,6 +140,7 @@ public function testSaveWithIndex(): void
         $store = new TaggableDoctrineDbalStore(
             $this->connection,
             DefaultEventSerializer::createFromPaths([__DIR__ . '/Events']),
+            (new AttributeEventRegistryFactory())->create([__DIR__ . '/Events']),
             clock: $this->clock,
             config: ['keep_index' => true],
         );
@@ -144,6 +150,7 @@ public function testSaveWithIndex(): void
         $store = new TaggableDoctrineDbalStore(
             $this->connection,
             DefaultEventSerializer::createFromPaths([__DIR__ . '/Events']),
+            (new AttributeEventRegistryFactory())->create([__DIR__ . '/Events']),
             clock: $this->clock,
         );
 
@@ -535,7 +542,7 @@ public function testTags(): void
         }
     }
 
-    public function testAppendAndQuery(): void
+    public function testAppendWithoutAppendCondition(): void
     {
         $profileId1 = ProfileId::generate();
         $profileId2 = ProfileId::generate();
@@ -558,30 +565,125 @@ public function testAppendAndQuery(): void
         ];
 
         $this->store->append($messages);
+        $this->expectedStream($messages);
+    }
 
-        $stream = null;
+    public function testQueryTags(): void
+    {
+        $profileId1 = ProfileId::generate();
+        $profileId2 = ProfileId::generate();
 
-        try {
-            $stream = $this->store->query(new Query(
-                new SubQuery(['profile:' . $profileId1->toString()]),
-            ));
+        $message1 = Message::create(new ProfileCreated($profileId1, 'test'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+            ->withHeader(new TagsHeader(['profile:' . $profileId1->toString()]));
+        $message2 = Message::create(new ProfileCreated($profileId2, 'test'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+            ->withHeader(new TagsHeader(['profile:' . $profileId2->toString()]));
+        $message3 = Message::create(new ExternEvent('test message'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new TagsHeader([
+                'profile:' . $profileId1->toString(),
+                'profile:' . $profileId2->toString(),
+            ]));
+
+        $this->store->append([$message1, $message2, $message3]);
+
+        $stream = $this->store->query(new Query(
+            new SubQuery(['profile:' . $profileId1->toString()]),
+        ));
+
+        $this->expectedStreamEquals([$message1, $message3], $stream);
+    }
 
-            $messages = iterator_to_array($stream);
+    public function testQueryEvents(): void
+    {
+        $profileId1 = ProfileId::generate();
+        $profileId2 = ProfileId::generate();
 
-            self::assertCount(2, $messages);
+        $message1 = Message::create(new ProfileCreated($profileId1, 'test'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+            ->withHeader(new TagsHeader(['profile:' . $profileId1->toString()]));
+        $message2 = Message::create(new ProfileCreated($profileId2, 'test'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+            ->withHeader(new TagsHeader(['profile:' . $profileId2->toString()]));
+        $message3 = Message::create(new ExternEvent('test message'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new TagsHeader([
+                'profile:' . $profileId1->toString(),
+                'profile:' . $profileId2->toString(),
+            ]));
+
+        $this->store->append([$message1, $message2, $message3]);
+
+        $stream = $this->store->query(new Query(
+            new SubQuery(events: [ProfileCreated::class]),
+        ));
+
+        $this->expectedStreamEquals([$message1, $message2], $stream);
+    }
 
-            self::assertEquals(
-                ['profile:' . $profileId1->toString()],
-                $messages[0]->header(TagsHeader::class)->tags,
-            );
+    public function testQueryTagAndEvent(): void
+    {
+        $profileId1 = ProfileId::generate();
+        $profileId2 = ProfileId::generate();
 
-            self::assertEquals(
-                ['profile:' . $profileId1->toString(), 'profile:' . $profileId2->toString()],
-                $messages[1]->header(TagsHeader::class)->tags,
-            );
-        } finally {
-            $stream?->close();
-        }
+        $message1 = Message::create(new ProfileCreated($profileId1, 'test'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+            ->withHeader(new TagsHeader(['profile:' . $profileId1->toString()]));
+        $message2 = Message::create(new ProfileCreated($profileId2, 'test'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+            ->withHeader(new TagsHeader(['profile:' . $profileId2->toString()]));
+        $message3 = Message::create(new ExternEvent('test message'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new TagsHeader([
+                'profile:' . $profileId1->toString(),
+                'profile:' . $profileId2->toString(),
+            ]));
+
+        $this->store->append([$message1, $message2, $message3]);
+
+        $stream = $this->store->query(new Query(
+            new SubQuery(['profile:' . $profileId1->toString()], [ProfileCreated::class]),
+        ));
+
+        $this->expectedStreamEquals([$message1], $stream);
+    }
+
+    public function testComplexQuery(): void
+    {
+        $profileId1 = ProfileId::generate();
+        $profileId2 = ProfileId::generate();
+
+        $message1 = Message::create(new ProfileCreated($profileId1, 'test'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+            ->withHeader(new TagsHeader(['profile:' . $profileId1->toString()]));
+        $message2 = Message::create(new ProfileCreated($profileId2, 'test'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+            ->withHeader(new TagsHeader(['profile:' . $profileId2->toString()]));
+        $message3 = Message::create(new ExternEvent('test message'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new TagsHeader([
+                'profile:' . $profileId1->toString(),
+                'profile:' . $profileId2->toString(),
+            ]));
+
+        $this->store->append([$message1, $message2, $message3]);
+
+        $stream = $this->store->query(new Query(
+            new SubQuery(['profile:' . $profileId1->toString()], [ProfileCreated::class]),
+            new SubQuery(['profile:' . $profileId2->toString()]),
+            new SubQuery(events: [ExternEvent::class]),
+        ));
+
+        $this->expectedStreamEquals([$message1, $message2, $message3], $stream);
     }
 
     public function testAppendRaceCondition(): void
@@ -622,6 +724,80 @@ public function testAppendRaceCondition(): void
         );
     }
 
+    public function testAppendRaceConditionEmptyQuery(): void
+    {
+        $profileId1 = ProfileId::generate();
+        $profileId2 = ProfileId::generate();
+
+        $messages = [
+            Message::create(new ProfileCreated($profileId1, 'test'))
+                ->withHeader(new StreamNameHeader('foo'))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+                ->withHeader(new TagsHeader(['profile:' . $profileId1->toString()])),
+            Message::create(new ProfileCreated($profileId2, 'test'))
+                ->withHeader(new StreamNameHeader('foo'))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+                ->withHeader(new TagsHeader(['profile:' . $profileId2->toString()])),
+        ];
+
+        $this->store->append($messages);
+
+        $messages = [
+            Message::create(new ExternEvent('test message'))
+                ->withHeader(new StreamNameHeader('foo'))
+                ->withHeader(new TagsHeader([
+                    'profile:' . $profileId1->toString(),
+                    'profile:' . $profileId2->toString(),
+                ])),
+        ];
+
+        $this->expectException(AppendConditionNotMet::class);
+
+        $this->store->append(
+            $messages,
+            new AppendCondition(
+                new Query(),
+                0,
+            ),
+        );
+    }
+
+    public function testAppendWithEmptyQuery(): void
+    {
+        $profileId1 = ProfileId::generate();
+        $profileId2 = ProfileId::generate();
+
+        $messages = [
+            Message::create(new ProfileCreated($profileId1, 'test'))
+                ->withHeader(new StreamNameHeader('foo'))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+                ->withHeader(new TagsHeader(['profile:' . $profileId1->toString()])),
+            Message::create(new ProfileCreated($profileId2, 'test'))
+                ->withHeader(new StreamNameHeader('foo'))
+                ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+                ->withHeader(new TagsHeader(['profile:' . $profileId2->toString()])),
+        ];
+
+        $this->store->append($messages);
+
+        $message = Message::create(new ExternEvent('test message'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new TagsHeader([
+                'profile:' . $profileId1->toString(),
+                'profile:' . $profileId2->toString(),
+            ]));
+
+        $this->store->append(
+            [$message],
+            new AppendCondition(
+                new Query(),
+                2,
+            ),
+        );
+
+        $this->expectedStream([...$messages, $message]);
+    }
+
     public function testStreams(): void
     {
         $profileId = ProfileId::fromString('0190e47e-77e9-7b90-bf62-08bbf0ab9b4b');
@@ -681,4 +857,37 @@ public function testRemove(): void
 
         self::assertEquals(['foo'], $streams);
     }
+
+    /** @param list<Message> $messages */
+    private function expectedStream(array $messages): void
+    {
+        $this->expectedStreamEquals($messages, $this->store->load());
+    }
+
+    /** @param list<Message> $expectedMessages */
+    private function expectedStreamEquals(array $expectedMessages, Stream $stream): void
+    {
+        $index = 0;
+
+        $messages = iterator_to_array($stream);
+
+        self::assertEquals(count($expectedMessages), count($messages), 'Expected and actual message count do not match');
+
+        foreach ($messages as $message) {
+            $expectedMessage = $expectedMessages[$index] ?? null;
+
+            if ($expectedMessage === null) {
+                throw new RuntimeException(sprintf('Expected message at index %d not found', $index));
+            }
+
+            $this->assertEquals(
+                $expectedMessage->header(StreamNameHeader::class)->streamName,
+                $message->header(StreamNameHeader::class)->streamName,
+            );
+
+            $this->assertEquals($expectedMessage->event(), $message->event());
+
+            ++$index;
+        }
+    }
 }

From a7da910ef57432421c3d0a2b9268be4356e31614 Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Tue, 12 Aug 2025 13:48:31 +0200
Subject: [PATCH 12/22] handle stream name query

---
 src/DCB/EventAppender.php                     |  6 ++-
 src/DCB/EventRouter.php                       |  6 +++
 src/DCB/StoreEventAppender.php                | 10 +++--
 src/Store/SubQuery.php                        | 14 ++++++-
 src/Store/TaggableDoctrineDbalStore.php       | 14 +++++--
 .../Store/TaggableDoctrineDbalStoreTest.php   | 40 +++++++++++++++++--
 6 files changed, 79 insertions(+), 11 deletions(-)

diff --git a/src/DCB/EventAppender.php b/src/DCB/EventAppender.php
index b0bc4cad..9284bafa 100644
--- a/src/DCB/EventAppender.php
+++ b/src/DCB/EventAppender.php
@@ -10,5 +10,9 @@
 interface EventAppender
 {
     /** @param iterable<object> $events */
-    public function append(iterable $events, AppendCondition|null $appendCondition = null): void;
+    public function append(
+        iterable $events,
+        AppendCondition|null $appendCondition = null,
+        string|null $streamName = null,
+    ): void;
 }
diff --git a/src/DCB/EventRouter.php b/src/DCB/EventRouter.php
index 2483fa83..89668d25 100644
--- a/src/DCB/EventRouter.php
+++ b/src/DCB/EventRouter.php
@@ -46,6 +46,7 @@ public function subQuery(): SubQuery
         return new SubQuery(
             $this->tagFilter(),
             $this->eventTypeFilter(),
+            $this->streamName(),
         );
     }
 
@@ -163,4 +164,9 @@ static function (ReflectionNamedType|ReflectionIntersectionType $reflectionType)
 
     /** @return list<string> */
     abstract public function tagFilter(): array;
+
+    public function streamName(): string|null
+    {
+        return null;
+    }
 }
diff --git a/src/DCB/StoreEventAppender.php b/src/DCB/StoreEventAppender.php
index cf7b1b0c..dd9343db 100644
--- a/src/DCB/StoreEventAppender.php
+++ b/src/DCB/StoreEventAppender.php
@@ -18,15 +18,19 @@ final class StoreEventAppender implements EventAppender
     public function __construct(
         private readonly AppendStore $store,
         private readonly EventTagExtractor $eventTagExtractor = new AttributeEventTagExtractor(),
+        private readonly string $defaultStreamName = 'main',
     ) {
     }
 
     /** @param iterable<object> $events */
-    public function append(iterable $events, AppendCondition|null $appendCondition = null): void
-    {
+    public function append(
+        iterable $events,
+        AppendCondition|null $appendCondition = null,
+        string|null $streamName = null,
+    ): void {
         $messages = array_map(
             fn (object $event) => Message::create($event)
-                ->withHeader(new StreamNameHeader('main'))
+                ->withHeader(new StreamNameHeader($streamName ?? $this->defaultStreamName))
                 ->withHeader(new TagsHeader($this->eventTagExtractor->extract($event))),
             $events,
         );
diff --git a/src/Store/SubQuery.php b/src/Store/SubQuery.php
index 2bd3e1fd..cbe8bb34 100644
--- a/src/Store/SubQuery.php
+++ b/src/Store/SubQuery.php
@@ -5,6 +5,7 @@
 namespace Patchlevel\EventSourcing\Store;
 
 use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
 use Patchlevel\EventSourcing\Store\Header\TagsHeader;
 
 use function array_diff;
@@ -21,6 +22,7 @@ final class SubQuery
     public function __construct(
         public readonly array $tags = [],
         public readonly array $events = [],
+        public readonly string|null $streamName = null,
     ) {
         sort($tags);
         sort($events);
@@ -36,6 +38,10 @@ public function match(Message $message): bool
             return false;
         }
 
+        if ($this->streamName !== null && $message->header(StreamNameHeader::class)->streamName !== $this->streamName) {
+            return false;
+        }
+
         if ($this->events !== [] && !in_array($message->event()::class, $this->events, true)) {
             return false;
         }
@@ -45,7 +51,8 @@ public function match(Message $message): bool
 
     public function equals(self $queryComponent): bool
     {
-        return $this->tags === $queryComponent->tags
+        return $this->streamName === $queryComponent->streamName
+            && $this->tags === $queryComponent->tags
             && $this->events === $queryComponent->events;
     }
 
@@ -57,4 +64,9 @@ private function isSubset(array $needle, array $haystack): bool
     {
         return empty(array_diff($needle, $haystack));
     }
+
+    public function empty(): bool
+    {
+        return $this->streamName === null && $this->tags === [] && $this->events === [];
+    }
 }
diff --git a/src/Store/TaggableDoctrineDbalStore.php b/src/Store/TaggableDoctrineDbalStore.php
index f2dde8ea..a9e82e31 100644
--- a/src/Store/TaggableDoctrineDbalStore.php
+++ b/src/Store/TaggableDoctrineDbalStore.php
@@ -113,6 +113,7 @@ public function __construct(
             'lock_id' => self::DEFAULT_LOCK_ID,
             'lock_timeout' => -1,
             'keep_index' => false,
+            'default_stream_name' => 'main',
         ], $config);
 
         $platform = $this->connection->getDatabasePlatform();
@@ -295,7 +296,7 @@ function () use ($messages): void {
 
                     $parameters[] = $message->hasHeader(StreamNameHeader::class)
                         ? $message->header(StreamNameHeader::class)->streamName
-                        : 'default';
+                        : $this->config['default_stream_name'];
 
                     $parameters[] = $message->hasHeader(PlayheadHeader::class)
                         ? $message->header(PlayheadHeader::class)->playhead
@@ -411,7 +412,7 @@ public function append(iterable $messages, AppendCondition|null $appendCondition
 
                 $parameters['stream' . $position] = $message->hasHeader(StreamNameHeader::class)
                     ? $message->header(StreamNameHeader::class)->streamName
-                    : 'default';
+                    : $this->config['default_stream_name'];
 
                 $parameters['playhead' . $position] = $message->hasHeader(PlayheadHeader::class)
                     ? $message->header(PlayheadHeader::class)->playhead
@@ -819,7 +820,7 @@ private function queryCondition(QueryBuilder $builder, Query $query): void
         $uniqueParameterGenerator = $this->uniqueParameterGenerator();
 
         foreach ($query->subQueries as $subQuery) {
-            if ($subQuery->tags === [] && $subQuery->events === []) {
+            if ($subQuery->empty()) {
                 continue;
             }
 
@@ -827,6 +828,13 @@ private function queryCondition(QueryBuilder $builder, Query $query): void
                 ->select('id')
                 ->from($this->config['table_name']);
 
+            if ($subQuery->streamName !== null) {
+                $streamNameParameterName = $uniqueParameterGenerator();
+
+                $subQueryBuilder->andWhere("stream = :{$streamNameParameterName}");
+                $builder->setParameter($streamNameParameterName, $subQuery->streamName);
+            }
+
             if ($subQuery->tags !== []) {
                 $tagParameterName = $uniqueParameterGenerator();
 
diff --git a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
index 094ecede..45c75db8 100644
--- a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
+++ b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
@@ -626,6 +626,36 @@ public function testQueryEvents(): void
         $this->expectedStreamEquals([$message1, $message2], $stream);
     }
 
+    public function testQueryStream(): void
+    {
+        $profileId1 = ProfileId::generate();
+        $profileId2 = ProfileId::generate();
+
+        $message1 = Message::create(new ProfileCreated($profileId1, 'test'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+            ->withHeader(new TagsHeader(['profile:' . $profileId1->toString()]));
+        $message2 = Message::create(new ProfileCreated($profileId2, 'test'))
+            ->withHeader(new StreamNameHeader('bar'))
+            ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+            ->withHeader(new TagsHeader(['profile:' . $profileId2->toString()]));
+        $message3 = Message::create(new ExternEvent('test message'))
+            ->withHeader(new StreamNameHeader('baz'))
+            ->withHeader(new TagsHeader([
+                'profile:' . $profileId1->toString(),
+                'profile:' . $profileId2->toString(),
+            ]));
+
+        $this->store->append([$message1, $message2, $message3]);
+
+        $stream = $this->store->query(new Query(
+            new SubQuery(streamName: 'foo'),
+            new SubQuery(streamName: 'baz'),
+        ));
+
+        $this->expectedStreamEquals([$message1, $message3], $stream);
+    }
+
     public function testQueryTagAndEvent(): void
     {
         $profileId1 = ProfileId::generate();
@@ -669,21 +699,25 @@ public function testComplexQuery(): void
             ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
             ->withHeader(new TagsHeader(['profile:' . $profileId2->toString()]));
         $message3 = Message::create(new ExternEvent('test message'))
-            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new StreamNameHeader('main'))
             ->withHeader(new TagsHeader([
                 'profile:' . $profileId1->toString(),
                 'profile:' . $profileId2->toString(),
             ]));
+        $message4 = Message::create(new ExternEvent('test message'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new TagsHeader([]));
 
-        $this->store->append([$message1, $message2, $message3]);
+        $this->store->append([$message1, $message2, $message3, $message4]);
 
         $stream = $this->store->query(new Query(
             new SubQuery(['profile:' . $profileId1->toString()], [ProfileCreated::class]),
             new SubQuery(['profile:' . $profileId2->toString()]),
             new SubQuery(events: [ExternEvent::class]),
+            new SubQuery(streamName: 'foo'),
         ));
 
-        $this->expectedStreamEquals([$message1, $message2, $message3], $stream);
+        $this->expectedStreamEquals([$message1, $message2, $message3, $message4], $stream);
     }
 
     public function testAppendRaceCondition(): void

From 72ee0a57598134c96f6443ede8f3a29fcf10ed47 Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Wed, 13 Aug 2025 09:48:16 +0200
Subject: [PATCH 13/22] fix phpstan errors

---
 Makefile                                      |  2 +-
 src/DCB/ApplyMethodDetectionError.php         | 83 +++++++++++++++++++
 src/DCB/CompositeProjection.php               | 10 ++-
 src/DCB/DecisionModel.php                     | 12 ++-
 src/DCB/EventAppender.php                     |  4 +-
 src/DCB/EventRouter.php                       | 33 +++++---
 src/DCB/Projection.php                        |  2 +-
 src/DCB/StoreEventAppender.php                |  4 +-
 src/Metadata/PropertyType.php                 | 58 -------------
 .../Normalizer/StringableNormalizer.php       |  6 ++
 src/Store/AppendConditionNotMet.php           |  2 +-
 src/Store/Query.php                           |  4 +-
 src/Store/TaggableDoctrineDbalStore.php       | 10 ++-
 src/Stringable.php                            |  1 +
 .../SimpleSetupTaggableStoreBench.php         |  2 +
 .../DynamicConsistencyBoundaryTest.php        |  2 +
 .../Store/TaggableDoctrineDbalStoreTest.php   |  2 +
 .../DCB/AttributeEventTagExtractorTest.php    |  2 +-
 18 files changed, 152 insertions(+), 87 deletions(-)
 create mode 100644 src/DCB/ApplyMethodDetectionError.php
 delete mode 100644 src/Metadata/PropertyType.php

diff --git a/Makefile b/Makefile
index 859c0b31..4d0a6568 100644
--- a/Makefile
+++ b/Makefile
@@ -26,7 +26,7 @@ phpstan-baseline: vendor
 
 .PHONY: psalm
 psalm: vendor                                                                   ## run psalm static code analyser
-	vendor/bin/psalm
+	php -d memory_limit=312M vendor/bin/psalm
 
 .PHONY: psalm-baseline
 psalm-baseline: vendor                                                          ## run psalm static code analyser
diff --git a/src/DCB/ApplyMethodDetectionError.php b/src/DCB/ApplyMethodDetectionError.php
new file mode 100644
index 00000000..dd0a4827
--- /dev/null
+++ b/src/DCB/ApplyMethodDetectionError.php
@@ -0,0 +1,83 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+use RuntimeException;
+
+use function get_debug_type;
+use function sprintf;
+
+/** @experimental */
+final class ApplyMethodDetectionError extends RuntimeException
+{
+    public static function duplicateEmptyApplyAttribute(string $methodName): self
+    {
+        return new self(
+            sprintf(
+                'The method "%s" has multiple #[Apply] attributes with an empty "event" argument. Only one is allowed.',
+                $methodName,
+            ),
+        );
+    }
+
+    public static function mixedApplyAttributeUsage(string $methodName): self
+    {
+        return new self(
+            sprintf(
+                'The method "%s" has an #[Apply] attribute with an empty "event" argument, but also has a non-empty "event" argument in another #[Apply] attribute. This is not allowed.',
+                $methodName,
+            ),
+        );
+    }
+
+    public static function argumentTypeIsNotAClass(string $methodName, mixed $value): self
+    {
+        return new self(
+            sprintf(
+                'The method "%s" has an #[Apply] attribute with an "event" argument that is not a class: %s.',
+                $methodName,
+                get_debug_type($value),
+            ),
+        );
+    }
+
+    /**
+     * @param class-string $class
+     * @param class-string $event
+     */
+    public static function duplicateApplyMethod(string $class, string $event, string $fistMethod, string $secondMethod): self
+    {
+        return new self(
+            sprintf(
+                'Two methods "%s" and "%s" on the class "%s" want to apply the same event "%s". Only one method can apply an event.',
+                $fistMethod,
+                $secondMethod,
+                $class,
+                $event,
+            ),
+        );
+    }
+
+    public static function parameterIsMissing(string $methodName, int $parameterNumber): self
+    {
+        return new self(
+            sprintf(
+                'The method "%s" has an #[Apply] attribute with an "event" argument, but the parameter #%d is missing.',
+                $methodName,
+                $parameterNumber,
+            ),
+        );
+    }
+
+    public static function argumentTypeIsMissing(string $methodName): self
+    {
+        return new self(
+            sprintf(
+                'The method "%s" has an #[Apply] attribute with an empty "event" argument. This is not allowed.',
+                $methodName,
+            ),
+        );
+    }
+}
diff --git a/src/DCB/CompositeProjection.php b/src/DCB/CompositeProjection.php
index 1880a6f4..e9d736a3 100644
--- a/src/DCB/CompositeProjection.php
+++ b/src/DCB/CompositeProjection.php
@@ -9,10 +9,7 @@
 
 use function array_map;
 
-/**
- * @experimental
- * @extends Projection<array<string, mixed>>
- */
+/** @experimental */
 final class CompositeProjection
 {
     /** @param array<string, Projection> $projections */
@@ -40,6 +37,11 @@ public function initialState(): array
         }, $this->projections);
     }
 
+    /**
+     * @param array<string, mixed> $state
+     *
+     * @return array<string, mixed>
+     */
     public function apply(mixed $state, Message $message): mixed
     {
         foreach ($this->projections as $name => $projection) {
diff --git a/src/DCB/DecisionModel.php b/src/DCB/DecisionModel.php
index 54fb942a..80d7d0cf 100644
--- a/src/DCB/DecisionModel.php
+++ b/src/DCB/DecisionModel.php
@@ -14,11 +14,12 @@
 /**
  * @experimental
  * @psalm-immutable
- * @implements ArrayAccess<string, mixed>
+ * @implements ArrayAccess<key-of<T>, value-of<T>>
+ * @template T as array<string, mixed>
  */
 final class DecisionModel implements ArrayAccess
 {
-    /** @param array<string, mixed> $state */
+    /** @param T $state */
     public function __construct(
         public readonly array $state,
         public readonly AppendCondition $appendCondition,
@@ -30,6 +31,13 @@ public function offsetExists(mixed $offset): bool
         return array_key_exists($offset, $this->state);
     }
 
+    /**
+     * @param TKey $offset
+     *
+     * @return T[TKey]
+     *
+     * @template TKey of key-of<T>
+     */
     public function offsetGet(mixed $offset): mixed
     {
         if (!$this->offsetExists($offset)) {
diff --git a/src/DCB/EventAppender.php b/src/DCB/EventAppender.php
index 9284bafa..9c05e44a 100644
--- a/src/DCB/EventAppender.php
+++ b/src/DCB/EventAppender.php
@@ -9,9 +9,9 @@
 /** @experimental */
 interface EventAppender
 {
-    /** @param iterable<object> $events */
+    /** @param list<object> $events */
     public function append(
-        iterable $events,
+        array $events,
         AppendCondition|null $appendCondition = null,
         string|null $streamName = null,
     ): void;
diff --git a/src/DCB/EventRouter.php b/src/DCB/EventRouter.php
index 89668d25..782dd50e 100644
--- a/src/DCB/EventRouter.php
+++ b/src/DCB/EventRouter.php
@@ -19,10 +19,14 @@
 use function array_merge;
 use function class_exists;
 
-/** @experimental */
+/**
+ * @experimental
+ * @require-implements Projection<S>
+ * @template S of mixed
+ */
 trait EventRouter
 {
-    /** @param array<class-string, string>|null $applyMethods */
+    /** @var array<class-string, string>|null $applyMethods */
     private array|null $applyMethods = null;
 
     public function apply(mixed $state, Message $message): mixed
@@ -35,6 +39,7 @@ public function apply(mixed $state, Message $message): mixed
         $applyMethods = $this->applyMethods();
 
         if (array_key_exists($event::class, $applyMethods)) {
+            /* @phpstan-ignore return.type */
             return $this->{$applyMethods[$event::class]}($state, $event);
         }
 
@@ -90,7 +95,9 @@ private function applyMethods(): array
                 }
 
                 if ($hasOneEmptyApply) {
-                    throw new DuplicateEmptyApplyAttribute($method->getName());
+                    throw ApplyMethodDetectionError::duplicateEmptyApplyAttribute(
+                        $method->getName(),
+                    );
                 }
 
                 $hasOneEmptyApply = true;
@@ -98,16 +105,22 @@ private function applyMethods(): array
             }
 
             if ($hasOneEmptyApply && $hasOneNonEmptyApply) {
-                throw new MixedApplyAttributeUsage($method->getName());
+                throw ApplyMethodDetectionError::mixedApplyAttributeUsage(
+                    $method->getName(),
+                );
             }
 
             foreach ($eventClasses as $eventClass) {
                 if (!class_exists($eventClass)) {
-                    throw new ArgumentTypeIsNotAClass($method->getName(), $eventClass);
+                    throw ApplyMethodDetectionError::argumentTypeIsNotAClass(
+                        $method->getName(),
+                        $eventClass,
+                    );
                 }
 
                 if (array_key_exists($eventClass, $this->applyMethods)) {
-                    throw new DuplicateApplyMethod(
+                    throw ApplyMethodDetectionError::duplicateApplyMethod(
+                        static::class,
                         $eventClass,
                         $this->applyMethods[$eventClass],
                         $method->getName(),
@@ -127,18 +140,18 @@ private function getEventClassesByPropertyTypes(ReflectionMethod $method): array
         $parameters = $method->getParameters();
 
         if (array_key_exists(1, $parameters) === false) {
-            throw new ParameterIsMissing($method->getName(), 1);
+            throw ApplyMethodDetectionError::parameterIsMissing($method->getName(), 1);
         }
 
         $propertyType = $parameters[1]->getType();
         $methodName = $method->getName();
 
         if ($propertyType === null) {
-            throw new ArgumentTypeIsMissing($methodName);
+            throw ApplyMethodDetectionError::argumentTypeIsMissing($methodName);
         }
 
         if ($propertyType instanceof ReflectionIntersectionType) {
-            throw new ArgumentTypeIsMissing($methodName);
+            throw ApplyMethodDetectionError::argumentTypeIsMissing($methodName);
         }
 
         if ($propertyType instanceof ReflectionNamedType) {
@@ -150,7 +163,7 @@ private function getEventClassesByPropertyTypes(ReflectionMethod $method): array
                 static function (ReflectionNamedType|ReflectionIntersectionType $reflectionType) use ($methodName,
                 ): string {
                     if ($reflectionType instanceof ReflectionIntersectionType) {
-                        throw new ArgumentTypeIsMissing($methodName);
+                        throw ApplyMethodDetectionError::argumentTypeIsMissing($methodName);
                     }
 
                     return $reflectionType->getName();
diff --git a/src/DCB/Projection.php b/src/DCB/Projection.php
index f519c6cd..67aeb3c4 100644
--- a/src/DCB/Projection.php
+++ b/src/DCB/Projection.php
@@ -9,7 +9,7 @@
 
 /**
  * @experimental
- * @template S as mixed
+ * @template S of mixed
  */
 interface Projection
 {
diff --git a/src/DCB/StoreEventAppender.php b/src/DCB/StoreEventAppender.php
index dd9343db..91a3fa7a 100644
--- a/src/DCB/StoreEventAppender.php
+++ b/src/DCB/StoreEventAppender.php
@@ -22,9 +22,9 @@ public function __construct(
     ) {
     }
 
-    /** @param iterable<object> $events */
+    /** @param list<object> $events */
     public function append(
-        iterable $events,
+        array $events,
         AppendCondition|null $appendCondition = null,
         string|null $streamName = null,
     ): void {
diff --git a/src/Metadata/PropertyType.php b/src/Metadata/PropertyType.php
deleted file mode 100644
index ccbf5513..00000000
--- a/src/Metadata/PropertyType.php
+++ /dev/null
@@ -1,58 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Patchlevel\EventSourcing\Metadata;
-
-use ReflectionParameter;
-use Symfony\Component\TypeInfo\Type;
-use Symfony\Component\TypeInfo\Type\ObjectType;
-use Symfony\Component\TypeInfo\Type\UnionType;
-use Symfony\Component\TypeInfo\TypeResolver\TypeResolver;
-
-use function array_map;
-
-class PropertyType
-{
-    private TypeResolver $typeResolver;
-
-    public function __construct()
-    {
-        $this->typeResolver = TypeResolver::create();
-    }
-
-    /**
-     * @param class-string $class
-     *
-     * @return array<string>
-     */
-    public function getEventClassesByPropertyTypes(ReflectionParameter $parameter): array
-    {
-        $propertyType = $parameter->getType();
-
-        if ($propertyType === null) {
-            throw new ArgumentTypeIsMissing($methodName);
-        }
-
-        $type = $this->typeResolver->resolve($propertyType);
-
-        if ($type instanceof ObjectType) {
-            return [$type->getClassName()];
-        }
-
-        if ($type instanceof UnionType) {
-            return array_map(
-                static function (Type $type): string {
-                    if ($type instanceof ObjectType) {
-                        return $type->getClassName();
-                    }
-
-                    throw new ArgumentTypeIsMissing($methodName);
-                },
-                $type->getTypes(),
-            );
-        }
-
-        throw new ArgumentTypeIsMissing($methodName);
-    }
-}
diff --git a/src/Serializer/Normalizer/StringableNormalizer.php b/src/Serializer/Normalizer/StringableNormalizer.php
index 13c51854..537bdbaf 100644
--- a/src/Serializer/Normalizer/StringableNormalizer.php
+++ b/src/Serializer/Normalizer/StringableNormalizer.php
@@ -13,8 +13,10 @@
 use Symfony\Component\TypeInfo\Type;
 use Symfony\Component\TypeInfo\Type\ObjectType;
 
+use function is_a;
 use function is_string;
 
+/** @experimental */
 #[Attribute(Attribute::TARGET_PROPERTY | Attribute::TARGET_CLASS)]
 final class StringableNormalizer implements Normalizer, TypeAwareNormalizer
 {
@@ -74,6 +76,10 @@ public function handleType(Type|null $type): void
             return;
         }
 
+        if (is_a($type->getClassName(), Stringable::class, true) === false) {
+            throw InvalidType::unsupportedType(Stringable::class, $type->getClassName());
+        }
+
         $this->stringableClass = $type->getClassName();
     }
 }
diff --git a/src/Store/AppendConditionNotMet.php b/src/Store/AppendConditionNotMet.php
index f0ad8d61..21a60818 100644
--- a/src/Store/AppendConditionNotMet.php
+++ b/src/Store/AppendConditionNotMet.php
@@ -5,7 +5,7 @@
 namespace Patchlevel\EventSourcing\Store;
 
 /** @experimental */
-class AppendConditionNotMet extends StoreException
+final class AppendConditionNotMet extends StoreException
 {
     public function __construct(
         public readonly AppendCondition $appendCondition,
diff --git a/src/Store/Query.php b/src/Store/Query.php
index 9099eccb..c40bd0f4 100644
--- a/src/Store/Query.php
+++ b/src/Store/Query.php
@@ -4,6 +4,8 @@
 
 namespace Patchlevel\EventSourcing\Store;
 
+use function array_values;
+
 /** @experimental */
 final class Query
 {
@@ -13,7 +15,7 @@ final class Query
     public function __construct(
         SubQuery ...$subQueries,
     ) {
-        $this->subQueries = $subQueries;
+        $this->subQueries = array_values($subQueries);
     }
 
     public function add(SubQuery $subQuery): self
diff --git a/src/Store/TaggableDoctrineDbalStore.php b/src/Store/TaggableDoctrineDbalStore.php
index a9e82e31..bd4ff42b 100644
--- a/src/Store/TaggableDoctrineDbalStore.php
+++ b/src/Store/TaggableDoctrineDbalStore.php
@@ -82,7 +82,7 @@ final class TaggableDoctrineDbalStore implements StreamStore, AppendStore, Subsc
 
     private readonly ClockInterface $clock;
 
-    /** @var array{table_name: string, locking: bool, lock_id: int, lock_timeout: int, keep_index: bool} */
+    /** @var array{table_name: string, locking: bool, lock_id: int, lock_timeout: int, keep_index: bool, default_stream_name: string} */
     private readonly array $config;
 
     private bool $hasLock = false;
@@ -95,7 +95,7 @@ final class TaggableDoctrineDbalStore implements StreamStore, AppendStore, Subsc
 
     private readonly bool $isSQLite;
 
-    /** @param array{table_name?: string, locking?: bool, lock_id?: int, lock_timeout?: int, keep_index?: bool} $config */
+    /** @param array{table_name?: string, locking?: bool, lock_id?: int, lock_timeout?: int, keep_index?: bool, default_stream_name?: string} $config */
     public function __construct(
         private readonly Connection $connection,
         private readonly EventSerializer $eventSerializer,
@@ -486,7 +486,7 @@ public function append(iterable $messages, AppendCondition|null $appendCondition
                 throw new UniqueConstraintViolation($e);
             }
 
-            if ($affectedRows === 0 && $appendCondition->highestSequenceNumber !== null) {
+            if ($affectedRows === 0 && $appendCondition && $appendCondition->highestSequenceNumber !== null) {
                 throw new AppendConditionNotMet($appendCondition);
             }
         });
@@ -805,7 +805,9 @@ private function uniqueParameterGenerator(): Closure
         return static function () {
             static $counter = 0;
 
-            return 'param' . ++$counter;
+            ++$counter;
+
+            return 'param' . $counter;
         };
     }
 
diff --git a/src/Stringable.php b/src/Stringable.php
index ec6e4679..eeb96725 100644
--- a/src/Stringable.php
+++ b/src/Stringable.php
@@ -6,6 +6,7 @@
 
 use Patchlevel\EventSourcing\Serializer\Normalizer\StringableNormalizer;
 
+/** @experimental */
 #[StringableNormalizer]
 interface Stringable
 {
diff --git a/tests/Benchmark/SimpleSetupTaggableStoreBench.php b/tests/Benchmark/SimpleSetupTaggableStoreBench.php
index c5c929b7..c70a889a 100644
--- a/tests/Benchmark/SimpleSetupTaggableStoreBench.php
+++ b/tests/Benchmark/SimpleSetupTaggableStoreBench.php
@@ -6,6 +6,7 @@
 
 use Patchlevel\EventSourcing\Aggregate\AggregateRootId;
 use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Metadata\Event\AttributeEventRegistryFactory;
 use Patchlevel\EventSourcing\Repository\DefaultRepository;
 use Patchlevel\EventSourcing\Repository\Repository;
 use Patchlevel\EventSourcing\Schema\DoctrineSchemaDirector;
@@ -33,6 +34,7 @@ public function setUp(): void
         $this->store = new TaggableDoctrineDbalStore(
             $connection,
             DefaultEventSerializer::createFromPaths([__DIR__ . '/BasicImplementation/Events']),
+            (new AttributeEventRegistryFactory())->create([__DIR__ . '/BasicImplementation/Events']),
         );
 
         $this->repository = new DefaultRepository($this->store, Profile::metadata());
diff --git a/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php b/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php
index 608d8af5..ceecea11 100644
--- a/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php
+++ b/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php
@@ -77,6 +77,8 @@ public function testCourse(): void
         $commandBus->dispatch(new SubscribeStudentToCourse($student1Id, $courseId));
         $commandBus->dispatch(new SubscribeStudentToCourse($student2Id, $courseId));
 
+        $stream = $store->load();
+
         $this->assertTrue(true);
     }
 
diff --git a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
index 45c75db8..4372e1ba 100644
--- a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
+++ b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
@@ -480,6 +480,8 @@ public function testLoadWithWildcard(): void
             $stream?->close();
         }
 
+        $stream = null;
+
         try {
             $stream = $this->store->load(new Criteria(new StreamCriterion('*-*')));
 
diff --git a/tests/Unit/DCB/AttributeEventTagExtractorTest.php b/tests/Unit/DCB/AttributeEventTagExtractorTest.php
index ce94bb3b..c6fe4f37 100644
--- a/tests/Unit/DCB/AttributeEventTagExtractorTest.php
+++ b/tests/Unit/DCB/AttributeEventTagExtractorTest.php
@@ -8,7 +8,7 @@
 use Patchlevel\EventSourcing\DCB\AttributeEventTagExtractor;
 use PHPUnit\Framework\TestCase;
 
-class AttributeEventTagExtractorTest extends TestCase
+final class AttributeEventTagExtractorTest extends TestCase
 {
     public function testExtractEmpty(): void
     {

From 41404df948b5214b65301269a3adaa064bd4c666 Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Wed, 13 Aug 2025 09:56:42 +0200
Subject: [PATCH 14/22] add default for generic type in event router

---
 src/DCB/EventRouter.php | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/DCB/EventRouter.php b/src/DCB/EventRouter.php
index 782dd50e..d7037cce 100644
--- a/src/DCB/EventRouter.php
+++ b/src/DCB/EventRouter.php
@@ -21,8 +21,8 @@
 
 /**
  * @experimental
- * @require-implements Projection<S>
- * @template S of mixed
+ * @require-implements Projection
+ * @template S = mixed
  */
 trait EventRouter
 {

From f6f4b09d88598a2c1940f065785a6f36184eb2c0 Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Wed, 13 Aug 2025 10:20:57 +0200
Subject: [PATCH 15/22] add event sourcing phpstan extension

---
 composer.json     |  1 +
 composer.lock     | 59 ++++++++++++++++++++++++++++++++++++++++++++++-
 phpstan.neon.dist |  1 +
 3 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/composer.json b/composer.json
index bab3d8c0..d758b950 100644
--- a/composer.json
+++ b/composer.json
@@ -41,6 +41,7 @@
     "infection/infection": "^0.29.12",
     "league/commonmark": "^2.6.1",
     "patchlevel/coding-standard": "^1.3.0",
+    "patchlevel/event-sourcing-phpstan-extension": "^1.0",
     "patchlevel/event-sourcing-psalm-plugin": "^3.1.0",
     "phpat/phpat": "^0.11.3",
     "phpbench/phpbench": "^1.4.1",
diff --git a/composer.lock b/composer.lock
index d2d175e4..63a7b235 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "e47b04b41df0b48268165ffc8e103455",
+    "content-hash": "1595ca16451b55640850494b54772098",
     "packages": [
         {
             "name": "brick/math",
@@ -5627,6 +5627,63 @@
             },
             "time": "2023-06-02T10:05:08+00:00"
         },
+        {
+            "name": "patchlevel/event-sourcing-phpstan-extension",
+            "version": "1.0.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/patchlevel/event-sourcing-phpstan-extension.git",
+                "reference": "fb72d87091a5ed55f8079c8b2bacdec2f547143c"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/patchlevel/event-sourcing-phpstan-extension/zipball/fb72d87091a5ed55f8079c8b2bacdec2f547143c",
+                "reference": "fb72d87091a5ed55f8079c8b2bacdec2f547143c",
+                "shasum": ""
+            },
+            "require": {
+                "php": "~8.1 || ~8.2 || ~8.3 || 8.4",
+                "phpstan/phpstan": "^2.1.20"
+            },
+            "require-dev": {
+                "patchlevel/coding-standard": "^1.3.0",
+                "patchlevel/event-sourcing": "dev-DCB",
+                "phpstan/phpstan-strict-rules": "^2.0.4",
+                "roave/security-advisories": "dev-master",
+                "symfony/var-dumper": "^7.0.0"
+            },
+            "type": "phpstan-extension",
+            "autoload": {
+                "psr-4": {
+                    "Patchlevel\\EventSourcingPHPStanExtension\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Daniel Badura",
+                    "email": "daniel.badura@patchlevel.de"
+                },
+                {
+                    "name": "David Badura",
+                    "email": "david.badura@patchlevel.de"
+                }
+            ],
+            "description": "phpstan extension for patchlevel/event-sourcing",
+            "homepage": "https://github.com/patchlevel/event-sourcing-phpstan-extension",
+            "keywords": [
+                "PHPStan",
+                "event-sourcing"
+            ],
+            "support": {
+                "issues": "https://github.com/patchlevel/event-sourcing-phpstan-extension/issues",
+                "source": "https://github.com/patchlevel/event-sourcing-phpstan-extension/tree/1.0.0"
+            },
+            "time": "2025-08-13T08:14:47+00:00"
+        },
         {
             "name": "patchlevel/event-sourcing-psalm-plugin",
             "version": "3.1.0",
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 689e71a1..c5c79651 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -2,6 +2,7 @@ includes:
 	- phpstan-baseline.neon
 	- vendor/phpstan/phpstan-phpunit/extension.neon
 	- vendor/phpat/phpat/extension.neon
+	- vendor/patchlevel/event-sourcing-phpstan-extension/extension.neon
 
 parameters:
 	level: max

From d4d51c6837fa9509a607d03bde802d5998c51d79 Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Wed, 13 Aug 2025 11:24:03 +0200
Subject: [PATCH 16/22] fix phpstan errors

---
 baseline.xml                                  | 52 ++++++++++++++++++
 phpstan-baseline.neon                         | 30 +++++++++++
 .../DynamicConsistencyBoundaryTest.php        | 35 ++++++++++--
 .../NextInvoiceNumberProjection.php           |  2 +
 .../Store/TaggableDoctrineDbalStoreTest.php   | 53 ++++---------------
 tests/PhpunitHelper.php                       | 49 +++++++++++++++++
 6 files changed, 174 insertions(+), 47 deletions(-)
 create mode 100644 tests/PhpunitHelper.php

diff --git a/baseline.xml b/baseline.xml
index 7a797cba..f8cb9485 100644
--- a/baseline.xml
+++ b/baseline.xml
@@ -33,6 +33,28 @@
       <code><![CDATA[setPrimaryKey]]></code>
     </DeprecatedMethod>
   </file>
+  <file src="src/DCB/AttributeEventTagExtractor.php">
+    <RiskyTruthyFalsyComparison>
+      <code><![CDATA[$attribute->hash]]></code>
+      <code><![CDATA[$attribute->prefix]]></code>
+    </RiskyTruthyFalsyComparison>
+  </file>
+  <file src="src/DCB/CompositeProjection.php">
+    <MissingClosureReturnType>
+      <code><![CDATA[static function (Projection $projection) {]]></code>
+    </MissingClosureReturnType>
+    <MixedAssignment>
+      <code><![CDATA[$state[$name]]]></code>
+    </MixedAssignment>
+  </file>
+  <file src="src/DCB/DecisionModel.php">
+    <ImplementedReturnTypeMismatch>
+      <code><![CDATA[T[TKey]]]></code>
+    </ImplementedReturnTypeMismatch>
+    <InvalidCast>
+      <code><![CDATA[$offset]]></code>
+    </InvalidCast>
+  </file>
   <file src="src/EventBus/AttributeListenerProvider.php">
     <MixedMethodCall>
       <code><![CDATA[$method->getName()]]></code>
@@ -109,6 +131,11 @@
       <code><![CDATA[$type->getClassName()]]></code>
     </PropertyTypeCoercion>
   </file>
+  <file src="src/Serializer/Normalizer/StringableNormalizer.php">
+    <PropertyTypeCoercion>
+      <code><![CDATA[$type->getClassName()]]></code>
+    </PropertyTypeCoercion>
+  </file>
   <file src="src/Serializer/Upcast/Upcast.php">
     <MixedAssignment>
       <code><![CDATA[$payload[$key]]]></code>
@@ -152,6 +179,31 @@
       <code><![CDATA[(int)$data['playhead']]]></code>
     </ArgumentTypeCoercion>
   </file>
+  <file src="src/Store/TaggableDoctrineDbalStore.php">
+    <MixedAssignment>
+      <code><![CDATA[$counter]]></code>
+    </MixedAssignment>
+    <MixedOperand>
+      <code><![CDATA[$counter]]></code>
+      <code><![CDATA[$counter]]></code>
+    </MixedOperand>
+  </file>
+  <file src="src/Store/TaggableDoctrineDbalStoreStream.php">
+    <ArgumentTypeCoercion>
+      <code><![CDATA[(int)$data['playhead']]]></code>
+    </ArgumentTypeCoercion>
+    <MixedArgument>
+      <code><![CDATA[json_decode($data['tags'], true, 512, JSON_THROW_ON_ERROR)]]></code>
+    </MixedArgument>
+  </file>
+  <file src="src/Subscription/Engine/DefaultSubscriptionEngine.php">
+    <DeprecatedInterface>
+      <code><![CDATA[SubscriberAccessor|null]]></code>
+    </DeprecatedInterface>
+    <DeprecatedMethod>
+      <code><![CDATA[realSubscriber]]></code>
+    </DeprecatedMethod>
+  </file>
   <file src="src/Subscription/Engine/GapResolverStoreMessageLoader.php">
     <InvalidReturnType>
       <code><![CDATA[Generator<int, Message>]]></code>
diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index e656e2c6..3aea54d9 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -108,6 +108,36 @@ parameters:
 			count: 1
 			path: src/Store/StreamDoctrineDbalStoreStream.php
 
+		-
+			message: '#^Cannot use \+\+ on mixed\.$#'
+			identifier: preInc.type
+			count: 1
+			path: src/Store/TaggableDoctrineDbalStore.php
+
+		-
+			message: '#^Method Patchlevel\\EventSourcing\\Store\\TaggableDoctrineDbalStoreStream\:\:current\(\) never returns null so it can be removed from the return type\.$#'
+			identifier: return.unusedType
+			count: 1
+			path: src/Store/TaggableDoctrineDbalStoreStream.php
+
+		-
+			message: '#^Parameter \#1 \$playhead of class Patchlevel\\EventSourcing\\Store\\Header\\PlayheadHeader constructor expects int\<1, max\>, int given\.$#'
+			identifier: argument.type
+			count: 1
+			path: src/Store/TaggableDoctrineDbalStoreStream.php
+
+		-
+			message: '#^Parameter \#1 \$tags of class Patchlevel\\EventSourcing\\Store\\Header\\TagsHeader constructor expects list\<string\>, mixed given\.$#'
+			identifier: argument.type
+			count: 1
+			path: src/Store/TaggableDoctrineDbalStoreStream.php
+
+		-
+			message: '#^Ternary operator condition is always true\.$#'
+			identifier: ternary.alwaysTrue
+			count: 1
+			path: src/Store/TaggableDoctrineDbalStoreStream.php
+
 		-
 			message: '#^Generator expects key type int, int\<1, max\>\|null given\.$#'
 			identifier: generator.keyType
diff --git a/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php b/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php
index ceecea11..93286f98 100644
--- a/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php
+++ b/tests/Integration/DynamicConsistencyBoundary/DynamicConsistencyBoundaryTest.php
@@ -9,27 +9,36 @@
 use Patchlevel\EventSourcing\CommandBus\SyncCommandBus;
 use Patchlevel\EventSourcing\DCB\StoreDecisionModelBuilder;
 use Patchlevel\EventSourcing\DCB\StoreEventAppender;
+use Patchlevel\EventSourcing\Message\Message;
 use Patchlevel\EventSourcing\Metadata\Event\AttributeEventRegistryFactory;
 use Patchlevel\EventSourcing\Schema\DoctrineSchemaDirector;
 use Patchlevel\EventSourcing\Serializer\DefaultEventSerializer;
+use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
 use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
 use Patchlevel\EventSourcing\Tests\DbalManager;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Command\ChangeCourseCapacity;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Command\DefineCourse;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Command\SubscribeStudentToCourse;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseCapacityChanged;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseDefined;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\StudentSubscribedToCourse;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Handler\ChangeCourseCapacityHandler;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Handler\DefineCourseHandler;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Handler\SubscribeStudentToCourseHandler;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\StudentId;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Command\CreateInvoice;
+use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Event\InvoiceCreated;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Handler\CreateInvoiceHandler;
+use Patchlevel\EventSourcing\Tests\PhpunitHelper;
 use PHPUnit\Framework\Attributes\CoversNothing;
 use PHPUnit\Framework\TestCase;
 
 #[CoversNothing]
 final class DynamicConsistencyBoundaryTest extends TestCase
 {
+    use PhpunitHelper;
+
     private Connection $connection;
 
     public function setUp(): void
@@ -77,9 +86,16 @@ public function testCourse(): void
         $commandBus->dispatch(new SubscribeStudentToCourse($student1Id, $courseId));
         $commandBus->dispatch(new SubscribeStudentToCourse($student2Id, $courseId));
 
-        $stream = $store->load();
-
-        $this->assertTrue(true);
+        self::assertStreamEquals([
+            Message::create(new CourseDefined($courseId, 10))
+                ->withHeader(new StreamNameHeader('main')),
+            Message::create(new CourseCapacityChanged($courseId, 2))
+                ->withHeader(new StreamNameHeader('main')),
+            Message::create(new StudentSubscribedToCourse($student1Id, $courseId))
+                ->withHeader(new StreamNameHeader('main')),
+            Message::create(new StudentSubscribedToCourse($student2Id, $courseId))
+                ->withHeader(new StreamNameHeader('main')),
+        ], $store->load());
     }
 
     public function testInvoice(): void
@@ -112,6 +128,17 @@ public function testInvoice(): void
         $commandBus->dispatch(new CreateInvoice(10));
         $commandBus->dispatch(new CreateInvoice(10));
 
-        $this->assertTrue(true);
+        self::assertStreamEquals([
+            Message::create(new InvoiceCreated(1, 10))
+                ->withHeader(new StreamNameHeader('main')),
+            Message::create(new InvoiceCreated(2, 10))
+                ->withHeader(new StreamNameHeader('main')),
+            Message::create(new InvoiceCreated(3, 10))
+                ->withHeader(new StreamNameHeader('main')),
+            Message::create(new InvoiceCreated(4, 10))
+                ->withHeader(new StreamNameHeader('main')),
+            Message::create(new InvoiceCreated(5, 10))
+                ->withHeader(new StreamNameHeader('main')),
+        ], $store->load());
     }
 }
diff --git a/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php b/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
index b474a916..b282cee9 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
@@ -4,6 +4,7 @@
 
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Projection;
 
+use Patchlevel\EventSourcing\Attribute\Apply;
 use Patchlevel\EventSourcing\DCB\EventRouter;
 use Patchlevel\EventSourcing\DCB\Projection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Event\InvoiceCreated;
@@ -23,6 +24,7 @@ public function initialState(): int
         return 1;
     }
 
+    #[Apply]
     public function applyInvoiceCreated(int $state, InvoiceCreated $event): int
     {
         return $state + 1;
diff --git a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
index 4372e1ba..f0e9c0a5 100644
--- a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
+++ b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
@@ -24,19 +24,17 @@
 use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
 use Patchlevel\EventSourcing\Store\Header\TagsHeader;
 use Patchlevel\EventSourcing\Store\Query;
-use Patchlevel\EventSourcing\Store\Stream;
 use Patchlevel\EventSourcing\Store\SubQuery;
 use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
 use Patchlevel\EventSourcing\Store\UniqueConstraintViolation;
 use Patchlevel\EventSourcing\Tests\DbalManager;
 use Patchlevel\EventSourcing\Tests\Integration\Store\Events\ExternEvent;
 use Patchlevel\EventSourcing\Tests\Integration\Store\Events\ProfileCreated;
+use Patchlevel\EventSourcing\Tests\PhpunitHelper;
 use PHPUnit\Framework\Attributes\CoversNothing;
 use PHPUnit\Framework\TestCase;
 use Psr\Clock\ClockInterface;
-use RuntimeException;
 
-use function count;
 use function iterator_to_array;
 use function json_decode;
 use function sprintf;
@@ -44,6 +42,8 @@
 #[CoversNothing]
 final class TaggableDoctrineDbalStoreTest extends TestCase
 {
+    use PhpunitHelper;
+
     private Connection $connection;
     private TaggableDoctrineDbalStore $store;
 
@@ -567,7 +567,7 @@ public function testAppendWithoutAppendCondition(): void
         ];
 
         $this->store->append($messages);
-        $this->expectedStream($messages);
+        self::assertStreamEquals($messages, $this->store->load());
     }
 
     public function testQueryTags(): void
@@ -596,7 +596,7 @@ public function testQueryTags(): void
             new SubQuery(['profile:' . $profileId1->toString()]),
         ));
 
-        $this->expectedStreamEquals([$message1, $message3], $stream);
+        self::assertStreamEquals([$message1, $message3], $stream);
     }
 
     public function testQueryEvents(): void
@@ -625,7 +625,7 @@ public function testQueryEvents(): void
             new SubQuery(events: [ProfileCreated::class]),
         ));
 
-        $this->expectedStreamEquals([$message1, $message2], $stream);
+        self::assertStreamEquals([$message1, $message2], $stream);
     }
 
     public function testQueryStream(): void
@@ -655,7 +655,7 @@ public function testQueryStream(): void
             new SubQuery(streamName: 'baz'),
         ));
 
-        $this->expectedStreamEquals([$message1, $message3], $stream);
+        self::assertStreamEquals([$message1, $message3], $stream);
     }
 
     public function testQueryTagAndEvent(): void
@@ -684,7 +684,7 @@ public function testQueryTagAndEvent(): void
             new SubQuery(['profile:' . $profileId1->toString()], [ProfileCreated::class]),
         ));
 
-        $this->expectedStreamEquals([$message1], $stream);
+        self::assertStreamEquals([$message1], $stream);
     }
 
     public function testComplexQuery(): void
@@ -719,7 +719,7 @@ public function testComplexQuery(): void
             new SubQuery(streamName: 'foo'),
         ));
 
-        $this->expectedStreamEquals([$message1, $message2, $message3, $message4], $stream);
+        self::assertStreamEquals([$message1, $message2, $message3, $message4], $stream);
     }
 
     public function testAppendRaceCondition(): void
@@ -831,7 +831,7 @@ public function testAppendWithEmptyQuery(): void
             ),
         );
 
-        $this->expectedStream([...$messages, $message]);
+        self::assertStreamEquals([...$messages, $message], $this->store->load());
     }
 
     public function testStreams(): void
@@ -893,37 +893,4 @@ public function testRemove(): void
 
         self::assertEquals(['foo'], $streams);
     }
-
-    /** @param list<Message> $messages */
-    private function expectedStream(array $messages): void
-    {
-        $this->expectedStreamEquals($messages, $this->store->load());
-    }
-
-    /** @param list<Message> $expectedMessages */
-    private function expectedStreamEquals(array $expectedMessages, Stream $stream): void
-    {
-        $index = 0;
-
-        $messages = iterator_to_array($stream);
-
-        self::assertEquals(count($expectedMessages), count($messages), 'Expected and actual message count do not match');
-
-        foreach ($messages as $message) {
-            $expectedMessage = $expectedMessages[$index] ?? null;
-
-            if ($expectedMessage === null) {
-                throw new RuntimeException(sprintf('Expected message at index %d not found', $index));
-            }
-
-            $this->assertEquals(
-                $expectedMessage->header(StreamNameHeader::class)->streamName,
-                $message->header(StreamNameHeader::class)->streamName,
-            );
-
-            $this->assertEquals($expectedMessage->event(), $message->event());
-
-            ++$index;
-        }
-    }
 }
diff --git a/tests/PhpunitHelper.php b/tests/PhpunitHelper.php
new file mode 100644
index 00000000..acbbb84d
--- /dev/null
+++ b/tests/PhpunitHelper.php
@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests;
+
+use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
+use Patchlevel\EventSourcing\Store\Stream;
+use RuntimeException;
+
+use function count;
+use function iterator_to_array;
+use function sprintf;
+
+/** @require-extends PHPUnit\Framework\Assert */
+trait PhpunitHelper
+{
+    /** @param list<Message> $expectedMessages */
+    public static function assertStreamEquals(array $expectedMessages, Stream $stream): void
+    {
+        $index = 0;
+
+        $messages = iterator_to_array($stream);
+
+        self::assertEquals(count($expectedMessages), count($messages), 'Expected and actual message count do not match');
+
+        foreach ($messages as $message) {
+            $expectedMessage = $expectedMessages[$index] ?? null;
+
+            if ($expectedMessage === null) {
+                throw new RuntimeException(sprintf('Expected message at index %d not found', $index));
+            }
+
+            self::assertEquals(
+                $expectedMessage->header(StreamNameHeader::class)->streamName,
+                $message->header(StreamNameHeader::class)->streamName,
+            );
+
+            self::assertEquals(
+                $expectedMessage->event(),
+                $message->event(),
+                sprintf('Event at index %d does not match expected event', $index),
+            );
+
+            ++$index;
+        }
+    }
+}

From fc7f16d20a9979ce2ad606556a9ba846223b257d Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Wed, 13 Aug 2025 16:13:20 +0200
Subject: [PATCH 17/22] add only last event filter

---
 src/CommandBus/InstantRetryCommandBus.php     |  3 +-
 src/DCB/EventRouter.php                       |  6 ++++
 src/Store/SubQuery.php                        |  8 ++++--
 src/Store/TaggableDoctrineDbalStore.php       |  9 ++++--
 .../NextInvoiceNumberProjection.php           |  7 ++++-
 .../Store/TaggableDoctrineDbalStoreTest.php   | 28 +++++++++++++++++++
 6 files changed, 54 insertions(+), 7 deletions(-)

diff --git a/src/CommandBus/InstantRetryCommandBus.php b/src/CommandBus/InstantRetryCommandBus.php
index 41ff60b4..e245c847 100644
--- a/src/CommandBus/InstantRetryCommandBus.php
+++ b/src/CommandBus/InstantRetryCommandBus.php
@@ -6,6 +6,7 @@
 
 use Patchlevel\EventSourcing\Attribute\InstantRetry;
 use Patchlevel\EventSourcing\Repository\AggregateOutdated;
+use Patchlevel\EventSourcing\Store\AppendConditionNotMet;
 use ReflectionClass;
 use Throwable;
 
@@ -20,7 +21,7 @@ final class InstantRetryCommandBus implements CommandBus
     public function __construct(
         private readonly CommandBus $commandBus,
         private readonly int $defaultMaxRetries = 3,
-        private readonly array $defaultExceptions = [AggregateOutdated::class],
+        private readonly array $defaultExceptions = [AggregateOutdated::class, AppendConditionNotMet::class],
     ) {
     }
 
diff --git a/src/DCB/EventRouter.php b/src/DCB/EventRouter.php
index d7037cce..46d198d5 100644
--- a/src/DCB/EventRouter.php
+++ b/src/DCB/EventRouter.php
@@ -52,6 +52,7 @@ public function subQuery(): SubQuery
             $this->tagFilter(),
             $this->eventTypeFilter(),
             $this->streamName(),
+            $this->lastEventIsEnough(),
         );
     }
 
@@ -182,4 +183,9 @@ public function streamName(): string|null
     {
         return null;
     }
+
+    public function lastEventIsEnough(): bool
+    {
+        return false;
+    }
 }
diff --git a/src/Store/SubQuery.php b/src/Store/SubQuery.php
index cbe8bb34..1e7f2c00 100644
--- a/src/Store/SubQuery.php
+++ b/src/Store/SubQuery.php
@@ -23,6 +23,7 @@ public function __construct(
         public readonly array $tags = [],
         public readonly array $events = [],
         public readonly string|null $streamName = null,
+        public readonly bool $onlyLastEvent = false,
     ) {
         sort($tags);
         sort($events);
@@ -53,7 +54,8 @@ public function equals(self $queryComponent): bool
     {
         return $this->streamName === $queryComponent->streamName
             && $this->tags === $queryComponent->tags
-            && $this->events === $queryComponent->events;
+            && $this->events === $queryComponent->events
+            && $this->onlyLastEvent === $queryComponent->onlyLastEvent;
     }
 
     /**
@@ -67,6 +69,8 @@ private function isSubset(array $needle, array $haystack): bool
 
     public function empty(): bool
     {
-        return $this->streamName === null && $this->tags === [] && $this->events === [];
+        return $this->streamName === null
+            && $this->tags === []
+            && $this->events === [];
     }
 }
diff --git a/src/Store/TaggableDoctrineDbalStore.php b/src/Store/TaggableDoctrineDbalStore.php
index bd4ff42b..7742214f 100644
--- a/src/Store/TaggableDoctrineDbalStore.php
+++ b/src/Store/TaggableDoctrineDbalStore.php
@@ -803,11 +803,10 @@ private function unlock(): void
     private function uniqueParameterGenerator(): Closure
     {
         return static function () {
+            /** @var int $counter */
             static $counter = 0;
 
-            ++$counter;
-
-            return 'param' . $counter;
+            return 'param' . ++$counter;
         };
     }
 
@@ -868,6 +867,10 @@ private function queryCondition(QueryBuilder $builder, Query $query): void
                 );
             }
 
+            if ($subQuery->onlyLastEvent) {
+                $subQueryBuilder->select('MAX(id) AS id');
+            }
+
             $subqueries[] = $subQueryBuilder->getSQL();
         }
 
diff --git a/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php b/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
index b282cee9..5cfb7c88 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
@@ -27,6 +27,11 @@ public function initialState(): int
     #[Apply]
     public function applyInvoiceCreated(int $state, InvoiceCreated $event): int
     {
-        return $state + 1;
+        return $event->invoiceNumber + 1;
+    }
+
+    public function lastEventIsEnough(): bool
+    {
+        return true;
     }
 }
diff --git a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
index f0e9c0a5..f61a0df3 100644
--- a/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
+++ b/tests/Integration/Store/TaggableDoctrineDbalStoreTest.php
@@ -687,6 +687,34 @@ public function testQueryTagAndEvent(): void
         self::assertStreamEquals([$message1], $stream);
     }
 
+    public function testOnlyLastEvent(): void
+    {
+        $profileId1 = ProfileId::generate();
+        $profileId2 = ProfileId::generate();
+
+        $message1 = Message::create(new ProfileCreated($profileId1, 'test'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+            ->withHeader(new TagsHeader(['profile:' . $profileId1->toString()]));
+        $message2 = Message::create(new ProfileCreated($profileId2, 'test'))
+            ->withHeader(new StreamNameHeader('foo'))
+            ->withHeader(new RecordedOnHeader(new DateTimeImmutable('2020-01-01 00:00:00')))
+            ->withHeader(new TagsHeader(['profile:' . $profileId2->toString()]));
+
+        $this->store->append([$message1, $message2]);
+
+        $stream = $this->store->query(
+            new Query(
+                new SubQuery(
+                    events: [ProfileCreated::class],
+                    onlyLastEvent: true,
+                ),
+            ),
+        );
+
+        self::assertStreamEquals([$message2], $stream);
+    }
+
     public function testComplexQuery(): void
     {
         $profileId1 = ProfileId::generate();

From b28303d954c086bbfd1ad4636d97cb35424bb129 Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Thu, 21 Aug 2025 20:46:20 +0200
Subject: [PATCH 18/22] refactor query optimization & add tests

---
 baseline.xml                                  |   9 -
 docs/pages/dynamic_consistency_boundary.md    | 527 ++++++++++++++++++
 src/DCB/AttributeEventTagExtractor.php        |   9 +-
 src/DCB/CompositeProjection.php               |  15 +-
 src/DCB/EventTagExtractorError.php            |  26 +
 src/Store/Query.php                           |  30 +-
 src/Store/SubQuery.php                        |  58 +-
 .../DCB/AttributeEventTagExtractorTest.php    |  34 ++
 tests/Unit/DCB/CompositeProjectionTest.php    | 101 ++++
 tests/Unit/DCB/DecisionModelTest.php          |  74 +++
 tests/Unit/Fixture/IncrementProjection.php    |  44 ++
 tests/Unit/Store/QueryTest.php                | 210 +++++++
 tests/Unit/Store/SubQueryTest.php             | 242 ++++++++
 13 files changed, 1327 insertions(+), 52 deletions(-)
 create mode 100644 src/DCB/EventTagExtractorError.php
 create mode 100644 tests/Unit/DCB/CompositeProjectionTest.php
 create mode 100644 tests/Unit/DCB/DecisionModelTest.php
 create mode 100644 tests/Unit/Fixture/IncrementProjection.php
 create mode 100644 tests/Unit/Store/QueryTest.php
 create mode 100644 tests/Unit/Store/SubQueryTest.php

diff --git a/baseline.xml b/baseline.xml
index f8cb9485..7759cbfc 100644
--- a/baseline.xml
+++ b/baseline.xml
@@ -179,15 +179,6 @@
       <code><![CDATA[(int)$data['playhead']]]></code>
     </ArgumentTypeCoercion>
   </file>
-  <file src="src/Store/TaggableDoctrineDbalStore.php">
-    <MixedAssignment>
-      <code><![CDATA[$counter]]></code>
-    </MixedAssignment>
-    <MixedOperand>
-      <code><![CDATA[$counter]]></code>
-      <code><![CDATA[$counter]]></code>
-    </MixedOperand>
-  </file>
   <file src="src/Store/TaggableDoctrineDbalStoreStream.php">
     <ArgumentTypeCoercion>
       <code><![CDATA[(int)$data['playhead']]]></code>
diff --git a/docs/pages/dynamic_consistency_boundary.md b/docs/pages/dynamic_consistency_boundary.md
index 7064df33..24194b96 100644
--- a/docs/pages/dynamic_consistency_boundary.md
+++ b/docs/pages/dynamic_consistency_boundary.md
@@ -1,2 +1,529 @@
 # Dynamic Consistency Boundary
 
+In our little DCB getting-started example, we decide things atomically across multiple event streams without loading aggregates.
+We keep the example small and show how to validate a course subscription and how to generate invoice numbers using the DCB API.
+
+!!! note
+
+    DCB is marked as experimental. APIs may change.
+
+## Define some events
+
+First we define the events that happen in our system.
+
+A course can be defined with a capacity:
+
+```php
+use Patchlevel\EventSourcing\Attribute\Event;
+use Patchlevel\EventSourcing\Attribute\EventTag;
+
+#[Event('course.defined')]
+final class CourseDefined
+{
+    public function __construct(
+        #[EventTag(prefix: 'course')]
+        public CourseId $courseId,
+        public int $capacity,
+    ) {
+    }
+}
+```
+A course capacity can change later:
+
+```php
+use Patchlevel\EventSourcing\Attribute\Event;
+use Patchlevel\EventSourcing\Attribute\EventTag;
+
+#[Event('course.capacity_changed')]
+final class CourseCapacityChanged
+{
+    public function __construct(
+        #[EventTag(prefix: 'course')]
+        public CourseId $courseId,
+        public int $capacity,
+    ) {
+    }
+}
+```
+A student can subscribe to a course. We tag the event with both student and course, so that DCB projections can select the exact subset of events:
+
+```php
+use Patchlevel\EventSourcing\Attribute\Event;
+use Patchlevel\EventSourcing\Attribute\EventTag;
+
+#[Event('course.student_subscribed')]
+final class StudentSubscribedToCourse
+{
+    public function __construct(
+        #[EventTag(prefix: 'student')]
+        public readonly StudentId $studentId,
+        #[EventTag(prefix: 'course')]
+        public readonly CourseId $courseId,
+    ) {
+    }
+}
+```
+And finally, an invoice can be created with a monotonically increasing number:
+
+```php
+use Patchlevel\EventSourcing\Attribute\Event;
+use Patchlevel\EventSourcing\Attribute\EventTag;
+
+#[Event('invoice.created')]
+final class InvoiceCreated
+{
+    public function __construct(
+        #[EventTag(prefix: 'invoice')]
+        public readonly int $invoiceNumber,
+        public readonly int $money,
+    ) {
+    }
+}
+```
+
+## Define projections
+
+DCB builds a tiny, purpose-built state just for the current decision using projections.
+A projection selects events via tags, processes those events and yields a small value.
+
+We use the EventRouter trait which wires `#[Apply]` methods and builds a SubQuery from filters.
+
+Course exists:
+
+```php
+use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\EventRouter;
+use Patchlevel\EventSourcing\DCB\Projection;
+
+/** @implements Projection<bool> */
+final class CourseExists implements Projection
+{
+    use EventRouter;
+
+    public function __construct(private readonly CourseId $courseId) {}
+
+    public function initialState(): bool
+    {
+        return false;
+    }
+
+    /** @return list<string> */
+    public function tagFilter(): array
+    {
+        return ["course:{$this->courseId->toString()}"];
+    }
+
+    #[Apply]
+    public function applyCourseDefined(bool $state, CourseDefined $event): bool
+    {
+        return true;
+    }
+}
+```
+
+Current capacity of a course:
+
+```php
+use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\EventRouter;
+use Patchlevel\EventSourcing\DCB\Projection;
+
+final class CourseCapacityProjection implements Projection
+{
+    use EventRouter;
+
+    public function __construct(private readonly CourseId $courseId) {}
+
+    public function initialState(): int
+    {
+        return 0;
+    }
+
+    /** @return list<string> */
+    public function tagFilter(): array
+    {
+        return ["course:{$this->courseId->toString()}"];
+    }
+
+    #[Apply]
+    public function applyCourseDefined(int $state, CourseDefined $event): int
+    {
+        return $event->capacity;
+    }
+
+    #[Apply]
+    public function applyCourseCapacityChanged(int $state, CourseCapacityChanged $event): int
+    {
+        return $event->capacity;
+    }
+}
+```
+
+Count subscriptions of a course:
+
+```php
+use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\EventRouter;
+use Patchlevel\EventSourcing\DCB\Projection;
+
+final class NumberOfCourseSubscriptionsProjection implements Projection
+{
+    use EventRouter;
+
+    public function __construct(private readonly CourseId $courseId) {}
+
+    public function initialState(): int
+    {
+        return 0;
+    }
+
+    /** @return list<string> */
+    public function tagFilter(): array
+    {
+        return ["course:{$this->courseId->toString()}"];
+    }
+
+    #[Apply]
+    public function applyStudentSubscribedToCourse(int $state, StudentSubscribedToCourse $event): int
+    {
+        return $state + 1;
+    }
+}
+```
+
+Count subscriptions of a student:
+
+```php
+use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\EventRouter;
+use Patchlevel\EventSourcing\DCB\Projection;
+
+final class NumberOfStudentSubscriptionsProjection implements Projection
+{
+    use EventRouter;
+
+    public function __construct(private readonly StudentId $studentId) {}
+
+    public function initialState(): int
+    {
+        return 0;
+    }
+
+    /** @return list<string> */
+    public function tagFilter(): array
+    {
+        return ["student:{$this->studentId->toString()}"];
+    }
+
+    #[Apply]
+    public function applyStudentSubscribedToCourse(int $state, StudentSubscribedToCourse $event): int
+    {
+        return $state + 1;
+    }
+}
+```
+
+Has the student already subscribed to this course:
+
+```php
+use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\EventRouter;
+use Patchlevel\EventSourcing\DCB\Projection;
+
+/** @implements Projection<bool> */
+final class StudentAlreadySubscribedProjection implements Projection
+{
+    use EventRouter;
+
+    public function __construct(
+        private readonly StudentId $studentId,
+        private readonly CourseId $courseId,
+    ) {}
+
+    public function initialState(): bool
+    {
+        return false;
+    }
+
+    /** @return list<string> */
+    public function tagFilter(): array
+    {
+        return [
+            "student:{$this->studentId->toString()}",
+            "course:{$this->courseId->toString()}",
+        ];
+    }
+
+    #[Apply]
+    public function applyStudentSubscribedToCourse(bool $state, StudentSubscribedToCourse $event): bool
+    {
+        return true;
+    }
+}
+```
+
+Next invoice number from the last event only:
+
+```php
+use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\EventRouter;
+use Patchlevel\EventSourcing\DCB\Projection;
+
+final class NextInvoiceNumberProjection implements Projection
+{
+    use EventRouter;
+
+    public function initialState(): int
+    {
+        return 1;
+    }
+
+    #[Apply]
+    public function applyInvoiceCreated(int $state, InvoiceCreated $event): int
+    {
+        return $event->invoiceNumber + 1;
+    }
+
+    public function lastEventIsEnough(): bool
+    {
+        return true; // optimize: only the last matching event is needed
+    }
+}
+```
+
+!!! tip
+
+    `#[Apply]` methods can be named freely. The second parameter’s type determines which event is routed.
+
+## Write handlers
+
+Now we can build decisions and append new events atomically by using the DecisionModelBuilder and EventAppender.
+
+Define a course only if it does not exist yet:
+
+```php
+use Patchlevel\EventSourcing\Attribute\Handle;
+use Patchlevel\EventSourcing\DCB\DecisionModelBuilder;
+use Patchlevel\EventSourcing\DCB\EventAppender;
+
+final class DefineCourseHandler
+{
+    public function __construct(
+        private readonly DecisionModelBuilder $decisionModelBuilder,
+        private readonly EventAppender $eventAppender,
+    ) {}
+
+    #[Handle]
+    public function __invoke(DefineCourse $command): void
+    {
+        $state = $this->decisionModelBuilder->build([
+            'courseExists' => new CourseExists($command->courseId),
+        ]);
+
+        if ($state['courseExists']) {
+            throw new RuntimeException('Course already exists');
+        }
+
+        $this->eventAppender->append([
+            new CourseDefined($command->courseId, $command->capacity),
+        ], $state->appendCondition);
+    }
+}
+```
+
+Change capacity if different:
+
+```php
+use Patchlevel\EventSourcing\Attribute\Handle;
+use Patchlevel\EventSourcing\DCB\DecisionModelBuilder;
+use Patchlevel\EventSourcing\DCB\EventAppender;
+
+final class ChangeCourseCapacityHandler
+{
+    public function __construct(
+        private readonly DecisionModelBuilder $decisionModelBuilder,
+        private readonly EventAppender $eventAppender,
+    ) {}
+
+    #[Handle]
+    public function __invoke(ChangeCourseCapacity $command): void
+    {
+        $state = $this->decisionModelBuilder->build([
+            'courseExists' => new CourseExists($command->courseId),
+            'courseCapacity' => new CourseCapacityProjection($command->courseId),
+        ]);
+
+        if (!$state['courseExists']) {
+            throw new RuntimeException('Course does not exist');
+        }
+
+        if ($state['courseCapacity'] === $command->capacity) {
+            return;
+        }
+
+        $this->eventAppender->append([
+            new CourseCapacityChanged($command->courseId, $command->capacity),
+        ], $state->appendCondition);
+    }
+}
+```
+
+Subscribe a student with multiple checks atomically:
+
+```php
+use Patchlevel\EventSourcing\Attribute\Handle;
+use Patchlevel\EventSourcing\DCB\DecisionModelBuilder;
+use Patchlevel\EventSourcing\DCB\EventAppender;
+
+final class SubscribeStudentToCourseHandler
+{
+    public function __construct(
+        private readonly DecisionModelBuilder $decisionModelBuilder,
+        private readonly EventAppender $eventAppender,
+    ) {}
+
+    #[Handle]
+    public function __invoke(SubscribeStudentToCourse $command): void
+    {
+        $state = $this->decisionModelBuilder->build([
+            'courseExists' => new CourseExists($command->courseId),
+            'courseCapacity' => new CourseCapacityProjection($command->courseId),
+            'numberOfCourseSubscriptions' => new NumberOfCourseSubscriptionsProjection($command->courseId),
+            'numberOfStudentSubscriptions' => new NumberOfStudentSubscriptionsProjection($command->studentId),
+            'studentAlreadySubscribed' => new StudentAlreadySubscribedProjection($command->studentId, $command->courseId),
+        ]);
+
+        if (!$state['courseExists']) {
+            throw new RuntimeException("Course {$command->courseId->toString()} does not exist");
+        }
+
+        if ($state['numberOfCourseSubscriptions'] >= $state['courseCapacity']) {
+            throw new RuntimeException("Course {$command->courseId->toString()} is not available");
+        }
+
+        if ($state['studentAlreadySubscribed']) {
+            throw new RuntimeException("Student {$command->studentId->toString()} is already subscribed to course {$command->courseId->toString()}");
+        }
+
+        if ($state['numberOfStudentSubscriptions'] >= 5) {
+            throw new RuntimeException("Student {$command->studentId->toString()} is already subscribed to 5 courses");
+        }
+
+        $this->eventAppender->append([
+            new StudentSubscribedToCourse($command->studentId, $command->courseId),
+        ], $state->appendCondition);
+    }
+}
+```
+
+Create invoices while safely generating the next number from the last event only:
+
+```php
+use Patchlevel\EventSourcing\Attribute\Handle;
+use Patchlevel\EventSourcing\DCB\DecisionModelBuilder;
+use Patchlevel\EventSourcing\DCB\EventAppender;
+
+final class CreateInvoiceHandler
+{
+    public function __construct(
+        private readonly DecisionModelBuilder $decisionModelBuilder,
+        private readonly EventAppender $eventAppender,
+    ) {}
+
+    #[Handle]
+    public function __invoke(CreateInvoice $command): void
+    {
+        $state = $this->decisionModelBuilder->build([
+            'nextInvoiceNumber' => new NextInvoiceNumberProjection(),
+        ]);
+
+        $this->eventAppender->append([
+            new InvoiceCreated($state['nextInvoiceNumber'], $command->money),
+        ], $state->appendCondition);
+    }
+}
+```
+
+!!! tip
+
+    If any concurrent writer changes the queried subset in between build() and append(), the store will reject the write (optimistic concurrency). You can retry if appropriate.
+
+## Configuration
+
+Now we plug the whole thing together. We use the TaggableDoctrineDbalStore plus the DCB builder and appender.
+
+```php
+use Patchlevel\EventSourcing\CommandBus\ServiceHandlerProvider;
+use Patchlevel\EventSourcing\CommandBus\SyncCommandBus;
+use Patchlevel\EventSourcing\DCB\StoreDecisionModelBuilder;
+use Patchlevel\EventSourcing\DCB\StoreEventAppender;
+use Patchlevel\EventSourcing\Metadata\Event\AttributeEventRegistryFactory;
+use Patchlevel\EventSourcing\Serializer\DefaultEventSerializer;
+use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
+
+$store = new TaggableDoctrineDbalStore(
+    $connection,
+    DefaultEventSerializer::createFromPaths([__DIR__ . '/Event']),
+    (new AttributeEventRegistryFactory())->create([__DIR__ . '/Event']),
+);
+
+$decisionModelBuilder = new StoreDecisionModelBuilder($store);
+$eventAppender = new StoreEventAppender($store);
+
+$commandBus = new SyncCommandBus(
+    new ServiceHandlerProvider([
+        new DefineCourseHandler($decisionModelBuilder, $eventAppender),
+        new ChangeCourseCapacityHandler($decisionModelBuilder, $eventAppender),
+        new SubscribeStudentToCourseHandler($decisionModelBuilder, $eventAppender),
+        new CreateInvoiceHandler($decisionModelBuilder, $eventAppender),
+    ]),
+);
+```
+
+## Database setup
+
+To actually write data to the database we need to create the event table.
+
+```php
+use Patchlevel\EventSourcing\Schema\DoctrineSchemaDirector;
+
+$schemaDirector = new DoctrineSchemaDirector($connection, $store);
+$schemaDirector->create();
+```
+
+!!! note
+
+    You can also use the predefined CLI commands to create and drop the schema. See the CLI documentation.
+
+## Usage
+
+We are now ready to use DCB. We can dispatch commands and DCB will keep each decision consistent.
+
+```php
+$courseId = CourseId::generate();
+$student1 = StudentId::generate();
+$student2 = StudentId::generate();
+
+$commandBus->dispatch(new DefineCourse($courseId, 10));
+$commandBus->dispatch(new ChangeCourseCapacity($courseId, 2));
+$commandBus->dispatch(new SubscribeStudentToCourse($student1, $courseId));
+$commandBus->dispatch(new SubscribeStudentToCourse($student2, $courseId));
+
+$commandBus->dispatch(new CreateInvoice(10));
+$commandBus->dispatch(new CreateInvoice(10));
+```
+
+## Result
+
+!!! success
+
+    We have successfully implemented and used DCB to make consistent decisions across multiple streams without loading aggregates.
+    Feel free to browse further in the documentation for more detailed information.
+
+## Learn more
+
+* [How to use command bus](command_bus.md)
+* [How to use aggregates](aggregate.md)
+* [How to use aggregate id](aggregate_id.md)
+* [How to use clock](clock.md)
+
diff --git a/src/DCB/AttributeEventTagExtractor.php b/src/DCB/AttributeEventTagExtractor.php
index 566c3010..30e869e8 100644
--- a/src/DCB/AttributeEventTagExtractor.php
+++ b/src/DCB/AttributeEventTagExtractor.php
@@ -7,15 +7,12 @@
 use Patchlevel\EventSourcing\Attribute\EventTag;
 use Patchlevel\EventSourcing\Stringable;
 use ReflectionClass;
-use RuntimeException;
 use Stringable as NativeStringable;
 
 use function array_keys;
-use function get_debug_type;
 use function hash;
 use function is_int;
 use function is_string;
-use function sprintf;
 
 /** @experimental */
 final class AttributeEventTagExtractor implements EventTagExtractor
@@ -48,8 +45,10 @@ public function extract(object $event): array
             }
 
             if (!is_string($value)) {
-                throw new RuntimeException(
-                    sprintf('Event tag value must be stringable, %s given', get_debug_type($value)),
+                throw EventTagExtractorError::invalidValueType(
+                    $event::class,
+                    $property->getName(),
+                    $value,
                 );
             }
 
diff --git a/src/DCB/CompositeProjection.php b/src/DCB/CompositeProjection.php
index e9d736a3..5976c390 100644
--- a/src/DCB/CompositeProjection.php
+++ b/src/DCB/CompositeProjection.php
@@ -20,13 +20,14 @@ public function __construct(
 
     public function query(): Query
     {
-        $query = new Query();
-
-        foreach ($this->projections as $projection) {
-            $query = $query->add($projection->subQuery());
-        }
-
-        return $query;
+        $query = new Query(
+            ...array_map(
+                static fn (Projection $projection) => $projection->subQuery(),
+                $this->projections,
+            ),
+        );
+
+        return $query->optimize();
     }
 
     /** @return array<string, mixed> */
diff --git a/src/DCB/EventTagExtractorError.php b/src/DCB/EventTagExtractorError.php
new file mode 100644
index 00000000..96185fc6
--- /dev/null
+++ b/src/DCB/EventTagExtractorError.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+use RuntimeException;
+
+use function get_debug_type;
+use function sprintf;
+
+final class EventTagExtractorError extends RuntimeException
+{
+    /** @param class-string $class */
+    public static function invalidValueType(string $class, string $property, mixed $value): self
+    {
+        return new self(
+            sprintf(
+                'Event tag value for property "%s" in class "%s" must be stringable, %s given',
+                $property,
+                $class,
+                get_debug_type($value),
+            ),
+        );
+    }
+}
diff --git a/src/Store/Query.php b/src/Store/Query.php
index c40bd0f4..217a0525 100644
--- a/src/Store/Query.php
+++ b/src/Store/Query.php
@@ -4,6 +4,7 @@
 
 namespace Patchlevel\EventSourcing\Store;
 
+use function array_merge;
 use function array_values;
 
 /** @experimental */
@@ -20,12 +21,33 @@ public function __construct(
 
     public function add(SubQuery $subQuery): self
     {
-        foreach ($this->subQueries as $query) {
-            if ($query->equals($subQuery)) {
-                return $this;
+        return new self(...array_merge($this->subQueries, [$subQuery]));
+    }
+
+    /**
+     * Optimize the query by removing sub-queries that are included in other sub-queries.
+     */
+    public function optimize(): Query
+    {
+        $queries = $this->subQueries;
+
+        foreach ($queries as $key => $a) {
+            foreach ($queries as $b) {
+                if ($a === $b) {
+                    continue;
+                }
+
+                if ($b->empty() && !$b->onlyLastEvent) {
+                    return new self();
+                }
+
+                if ($b->includes($a)) {
+                    unset($queries[$key]);
+                    continue 2;
+                }
             }
         }
 
-        return new self($subQuery, ...$this->subQueries);
+        return new self(...$queries);
     }
 }
diff --git a/src/Store/SubQuery.php b/src/Store/SubQuery.php
index 1e7f2c00..d4513191 100644
--- a/src/Store/SubQuery.php
+++ b/src/Store/SubQuery.php
@@ -10,7 +10,6 @@
 
 use function array_diff;
 use function in_array;
-use function sort;
 
 /** @experimental */
 final class SubQuery
@@ -25,52 +24,57 @@ public function __construct(
         public readonly string|null $streamName = null,
         public readonly bool $onlyLastEvent = false,
     ) {
-        sort($tags);
-        sort($events);
     }
 
     public function match(Message $message): bool
     {
-        if ($this->tags === [] && $this->events === []) {
-            return true;
+        if (
+            $this->streamName !== null
+            && (!$message->hasHeader(StreamNameHeader::class)
+                || $message->header(StreamNameHeader::class)->streamName !== $this->streamName)
+        ) {
+            return false;
         }
 
-        if (!$message->hasHeader(TagsHeader::class)) {
+        if (
+            $this->tags !== []
+            && (!$message->hasHeader(TagsHeader::class)
+                || !self::isSubset($this->tags, $message->header(TagsHeader::class)->tags))
+        ) {
             return false;
         }
 
-        if ($this->streamName !== null && $message->header(StreamNameHeader::class)->streamName !== $this->streamName) {
+        return $this->events === [] || in_array($message->event()::class, $this->events, true);
+    }
+
+    public function empty(): bool
+    {
+        return $this->streamName === null && $this->tags === [] && $this->events === [];
+    }
+
+    public function includes(SubQuery $other): bool
+    {
+        if ($this->streamName !== null && $this->streamName !== $other->streamName) {
             return false;
         }
 
-        if ($this->events !== [] && !in_array($message->event()::class, $this->events, true)) {
+        if (!self::isSubset($this->tags, $other->tags)) {
             return false;
         }
 
-        return $this->isSubset($this->tags, $message->header(TagsHeader::class)->tags);
-    }
+        if (!self::isSubset($this->events, $other->events)) {
+            return false;
+        }
 
-    public function equals(self $queryComponent): bool
-    {
-        return $this->streamName === $queryComponent->streamName
-            && $this->tags === $queryComponent->tags
-            && $this->events === $queryComponent->events
-            && $this->onlyLastEvent === $queryComponent->onlyLastEvent;
+        return !$this->onlyLastEvent || $other->onlyLastEvent;
     }
 
     /**
-     * @param list<string> $needle
-     * @param list<string> $haystack
+     * @param list<string> $subject
+     * @param list<string> $off
      */
-    private function isSubset(array $needle, array $haystack): bool
-    {
-        return empty(array_diff($needle, $haystack));
-    }
-
-    public function empty(): bool
+    private static function isSubset(array $subject, array $off): bool
     {
-        return $this->streamName === null
-            && $this->tags === []
-            && $this->events === [];
+        return empty(array_diff($subject, $off));
     }
 }
diff --git a/tests/Unit/DCB/AttributeEventTagExtractorTest.php b/tests/Unit/DCB/AttributeEventTagExtractorTest.php
index c6fe4f37..84afd8c6 100644
--- a/tests/Unit/DCB/AttributeEventTagExtractorTest.php
+++ b/tests/Unit/DCB/AttributeEventTagExtractorTest.php
@@ -4,6 +4,7 @@
 
 namespace Patchlevel\EventSourcing\Tests\Unit\DCB;
 
+use Patchlevel\EventSourcing\Aggregate\CustomId;
 use Patchlevel\EventSourcing\Attribute\EventTag;
 use Patchlevel\EventSourcing\DCB\AttributeEventTagExtractor;
 use PHPUnit\Framework\TestCase;
@@ -22,6 +23,22 @@ public function testExtractEmpty(): void
         self::assertSame([], $tags);
     }
 
+    public function testExtractClassWithoutAttributes(): void
+    {
+        $extractor = new AttributeEventTagExtractor();
+
+        $event = new class {
+            public function __construct(
+                public string $name = 'baz',
+            ) {
+            }
+        };
+
+        $tags = $extractor->extract($event);
+
+        self::assertSame([], $tags);
+    }
+
     public function testExtract(): void
     {
         $extractor = new AttributeEventTagExtractor();
@@ -41,6 +58,23 @@ public function __construct(
         self::assertSame(['foo', 'bar:baz'], $tags);
     }
 
+    public function testExtractStringable(): void
+    {
+        $extractor = new AttributeEventTagExtractor();
+
+        $event = new class (new CustomId('foo')) {
+            public function __construct(
+                #[EventTag]
+                public CustomId $id,
+            ) {
+            }
+        };
+
+        $tags = $extractor->extract($event);
+
+        self::assertSame(['foo'], $tags);
+    }
+
     public function testExtractWithHash(): void
     {
         $extractor = new AttributeEventTagExtractor();
diff --git a/tests/Unit/DCB/CompositeProjectionTest.php b/tests/Unit/DCB/CompositeProjectionTest.php
new file mode 100644
index 00000000..ed5b9724
--- /dev/null
+++ b/tests/Unit/DCB/CompositeProjectionTest.php
@@ -0,0 +1,101 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Unit\DCB;
+
+use Patchlevel\EventSourcing\DCB\CompositeProjection;
+use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
+use Patchlevel\EventSourcing\Store\Header\TagsHeader;
+use Patchlevel\EventSourcing\Store\Query;
+use Patchlevel\EventSourcing\Store\SubQuery;
+use Patchlevel\EventSourcing\Tests\Unit\Fixture\Email;
+use Patchlevel\EventSourcing\Tests\Unit\Fixture\IncrementProjection;
+use Patchlevel\EventSourcing\Tests\Unit\Fixture\ProfileCreated;
+use Patchlevel\EventSourcing\Tests\Unit\Fixture\ProfileId;
+use PHPUnit\Framework\TestCase;
+
+final class CompositeProjectionTest extends TestCase
+{
+    public function testQueryAggregatesSubQueries(): void
+    {
+        $p1 = new IncrementProjection(0, ['tag:a']);
+        $p2 = new IncrementProjection(0, ['tag:b'], 'main');
+
+        $composite = new CompositeProjection([
+            'a' => $p1,
+            'b' => $p2,
+        ]);
+
+        self::assertEquals(new Query(
+            new SubQuery(
+                ['tag:a'],
+                [ProfileCreated::class],
+            ),
+            new SubQuery(
+                ['tag:b'],
+                [ProfileCreated::class],
+                'main',
+            ),
+        ), $composite->query());
+    }
+
+    public function testInitialStateBuildsMap(): void
+    {
+        $composite = new CompositeProjection([
+            'alpha' => new IncrementProjection(1),
+            'beta' => new IncrementProjection(5),
+        ]);
+
+        $state = $composite->initialState();
+
+        self::assertSame(['alpha' => 1, 'beta' => 5], $state);
+    }
+
+    public function testApplyDelegatesToEachProjection(): void
+    {
+        $composite = new CompositeProjection([
+            'x' => new IncrementProjection(0, ['match']),
+            'y' => new IncrementProjection(10, ['match']),
+        ]);
+
+        $state = $composite->initialState();
+
+        $message = Message::create(new ProfileCreated(
+            ProfileId::fromString('test'),
+            Email::fromString('foo@example.com'),
+        ))
+            ->withHeader(new StreamNameHeader('main'))
+            ->withHeader(new TagsHeader(['match']));
+
+        $newState = $composite->apply($state, $message);
+
+        // both should have been incremented by 1
+        self::assertSame(1, $newState['x']);
+        self::assertSame(11, $newState['y']);
+    }
+
+    public function testApplySkipsNonMatchingProjection(): void
+    {
+        $composite = new CompositeProjection([
+            'm' => new IncrementProjection(2, ['match']),
+            'n' => new IncrementProjection(3, ['other']),
+        ]);
+
+        $state = $composite->initialState();
+
+        $message = Message::create(new ProfileCreated(
+            ProfileId::fromString('test'),
+            Email::fromString('foo@example.com'),
+        ))
+            ->withHeader(new StreamNameHeader('main'))
+            ->withHeader(new TagsHeader(['match']));
+
+        $newState = $composite->apply($state, $message);
+
+        // 'm' matches and increments; 'n' does not match and stays the same
+        self::assertSame(3, $newState['m']);
+        self::assertSame(3, $newState['n']);
+    }
+}
diff --git a/tests/Unit/DCB/DecisionModelTest.php b/tests/Unit/DCB/DecisionModelTest.php
new file mode 100644
index 00000000..fb8718b6
--- /dev/null
+++ b/tests/Unit/DCB/DecisionModelTest.php
@@ -0,0 +1,74 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Unit\DCB;
+
+use LogicException;
+use OutOfBoundsException;
+use Patchlevel\EventSourcing\DCB\DecisionModel;
+use Patchlevel\EventSourcing\Store\AppendCondition;
+use Patchlevel\EventSourcing\Store\Query;
+use Patchlevel\EventSourcing\Store\SubQuery;
+use PHPUnit\Framework\TestCase;
+
+final class DecisionModelTest extends TestCase
+{
+    private function createAppendCondition(): AppendCondition
+    {
+        $query = new Query(new SubQuery(['tag:foo']));
+
+        return new AppendCondition($query, 42);
+    }
+
+    public function testArrayAccessGetAndAppendCondition(): void
+    {
+        $appendCondition = $this->createAppendCondition();
+
+        $model = new DecisionModel([
+            'foo' => 123,
+            'bar' => 'baz',
+        ], $appendCondition);
+
+        self::assertSame(123, $model['foo']);
+        self::assertSame('baz', $model['bar']);
+        self::assertSame($appendCondition, $model->appendCondition);
+    }
+
+    public function testOffsetExists(): void
+    {
+        $model = new DecisionModel(['a' => 1], $this->createAppendCondition());
+
+        self::assertTrue(isset($model['a']));
+        /** @phpstan-ignore-next-line */
+        self::assertFalse(isset($model['b']));
+    }
+
+    public function testUnknownKeyThrowsOutOfBounds(): void
+    {
+        $model = new DecisionModel(['a' => 1], $this->createAppendCondition());
+
+        $this->expectException(OutOfBoundsException::class);
+        // access non-existing key
+        /** @phpstan-ignore-next-line */
+        $unused = $model['b'];
+    }
+
+    public function testImmutableSetThrows(): void
+    {
+        $model = new DecisionModel(['a' => 1], $this->createAppendCondition());
+
+        $this->expectException(LogicException::class);
+        /** @phpstan-ignore-next-line */
+        $model['a'] = 2;
+    }
+
+    public function testImmutableUnsetThrows(): void
+    {
+        $model = new DecisionModel(['a' => 1], $this->createAppendCondition());
+
+        $this->expectException(LogicException::class);
+        /** @phpstan-ignore-next-line */
+        unset($model['a']);
+    }
+}
diff --git a/tests/Unit/Fixture/IncrementProjection.php b/tests/Unit/Fixture/IncrementProjection.php
new file mode 100644
index 00000000..ced2180d
--- /dev/null
+++ b/tests/Unit/Fixture/IncrementProjection.php
@@ -0,0 +1,44 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Unit\Fixture;
+
+use Patchlevel\EventSourcing\Attribute\Apply;
+use Patchlevel\EventSourcing\DCB\EventRouter;
+use Patchlevel\EventSourcing\DCB\Projection;
+
+final class IncrementProjection implements Projection
+{
+    use EventRouter;
+
+    /** @param list<string> $tags */
+    public function __construct(
+        private readonly int $initial,
+        private readonly array $tags = [],
+        private readonly string|null $streamName = null,
+    ) {
+    }
+
+    #[Apply]
+    public function applyProfileCreated(int $state, ProfileCreated $event): int
+    {
+        return $state + 1;
+    }
+
+    public function initialState(): int
+    {
+        return $this->initial;
+    }
+
+    /** @return list<string> */
+    public function tagFilter(): array
+    {
+        return $this->tags;
+    }
+
+    public function streamName(): string|null
+    {
+        return $this->streamName;
+    }
+}
diff --git a/tests/Unit/Store/QueryTest.php b/tests/Unit/Store/QueryTest.php
new file mode 100644
index 00000000..f8cd4a9c
--- /dev/null
+++ b/tests/Unit/Store/QueryTest.php
@@ -0,0 +1,210 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Unit\Store;
+
+use Generator;
+use Patchlevel\EventSourcing\Store\Query;
+use Patchlevel\EventSourcing\Store\SubQuery;
+use Patchlevel\EventSourcing\Tests\Unit\Fixture\ProfileCreated;
+use Patchlevel\EventSourcing\Tests\Unit\Fixture\ProfileVisited;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+
+final class QueryTest extends TestCase
+{
+    public function testEmptyByDefault(): void
+    {
+        $query = new Query();
+
+        self::assertSame([], $query->subQueries);
+    }
+
+    public function testConstructWithSubqueriesKeepsOrder(): void
+    {
+        $sq1 = new SubQuery(['a'], [ProfileCreated::class], 's1');
+        $sq2 = new SubQuery(['b'], [ProfileVisited::class], 's2', true);
+
+        $query = new Query($sq1, $sq2);
+
+        self::assertEquals([$sq1, $sq2], $query->subQueries);
+    }
+
+    public function testAdd(): void
+    {
+        $sq1 = new SubQuery(['a'], [ProfileCreated::class], 's1');
+        $sq2 = new SubQuery(['b'], [ProfileVisited::class], 's2');
+
+        $q1 = new Query($sq1);
+        $q2 = $q1->add($sq2);
+
+        self::assertNotSame($q1, $q2);
+        self::assertEquals([$sq1, $sq2], $q2->subQueries);
+    }
+
+    #[DataProvider('providerForOptimize')]
+    public function testOptimize(Query $before, Query $after): void
+    {
+        self::assertEquals($after, $before->optimize());
+    }
+
+    /** @return Generator<string, array{Query, Query}> */
+    public static function providerForOptimize(): Generator
+    {
+        yield 'no subqueries' => [
+            new Query(),
+            new Query(),
+        ];
+
+        yield 'single subquery' => [
+            new Query(
+                new SubQuery(
+                    ['a'],
+                    [ProfileCreated::class],
+                    's1',
+                ),
+            ),
+            new Query(
+                new SubQuery(
+                    ['a'],
+                    [ProfileCreated::class],
+                    's1',
+                ),
+            ),
+        ];
+
+        yield 'equal subqueries' => [
+            new Query(
+                new SubQuery(
+                    ['a'],
+                    [ProfileCreated::class],
+                    's1',
+                ),
+                new SubQuery(
+                    ['a'],
+                    [ProfileCreated::class],
+                    's1',
+                ),
+            ),
+            new Query(
+                new SubQuery(
+                    ['a'],
+                    [ProfileCreated::class],
+                    's1',
+                ),
+            ),
+        ];
+
+        yield 'equal subqueries 3 times' => [
+            new Query(
+                new SubQuery(
+                    ['a'],
+                    [ProfileCreated::class],
+                    's1',
+                ),
+                new SubQuery(
+                    ['a'],
+                    [ProfileCreated::class],
+                    's1',
+                ),
+                new SubQuery(
+                    ['a'],
+                    [ProfileCreated::class],
+                    's1',
+                ),
+            ),
+            new Query(
+                new SubQuery(
+                    ['a'],
+                    [ProfileCreated::class],
+                    's1',
+                ),
+            ),
+        ];
+
+        yield 'empty sub query includes all' => [
+            new Query(
+                new SubQuery(
+                    ['a'],
+                    [ProfileCreated::class],
+                    's1',
+                ),
+                new SubQuery(
+                    ['b'],
+                    [ProfileVisited::class],
+                    's2',
+                    true,
+                ),
+                new SubQuery(),
+            ),
+            new Query(),
+        ];
+
+        yield 'partial overlap subqueries' => [
+            new Query(
+                new SubQuery(
+                    ['a'],
+                    [ProfileCreated::class],
+                ),
+                new SubQuery(
+                    ['a'],
+                ),
+                new SubQuery(
+                    [],
+                    [ProfileCreated::class],
+                ),
+            ),
+            new Query(
+                new SubQuery(
+                    ['a'],
+                ),
+                new SubQuery(
+                    [],
+                    [ProfileCreated::class],
+                ),
+            ),
+        ];
+
+        yield 'empty sub query' => [
+            new Query(
+                new SubQuery(),
+                new SubQuery(
+                    ['a'],
+                ),
+                new SubQuery(
+                    [],
+                    [ProfileCreated::class],
+                ),
+            ),
+            new Query(),
+        ];
+
+        yield 'empty sub query with only last event' => [
+            new Query(
+                new SubQuery(
+                    onlyLastEvent: true,
+                ),
+                new SubQuery(
+                    ['a'],
+                ),
+                new SubQuery(
+                    [],
+                    [ProfileCreated::class],
+                ),
+            ),
+            new Query(
+                new SubQuery(
+                    onlyLastEvent: true,
+                ),
+                new SubQuery(
+                    ['a'],
+                ),
+                new SubQuery(
+                    [],
+                    [ProfileCreated::class],
+                ),
+            ),
+        ];
+    }
+}
diff --git a/tests/Unit/Store/SubQueryTest.php b/tests/Unit/Store/SubQueryTest.php
new file mode 100644
index 00000000..e0db8398
--- /dev/null
+++ b/tests/Unit/Store/SubQueryTest.php
@@ -0,0 +1,242 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Unit\Store;
+
+use Generator;
+use InvalidArgumentException;
+use Patchlevel\EventSourcing\Message\Message;
+use Patchlevel\EventSourcing\Store\Header\StreamNameHeader;
+use Patchlevel\EventSourcing\Store\Header\TagsHeader;
+use Patchlevel\EventSourcing\Store\SubQuery;
+use Patchlevel\EventSourcing\Tests\Unit\Fixture\Email;
+use Patchlevel\EventSourcing\Tests\Unit\Fixture\ProfileCreated;
+use Patchlevel\EventSourcing\Tests\Unit\Fixture\ProfileId;
+use Patchlevel\EventSourcing\Tests\Unit\Fixture\ProfileVisited;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+
+final class SubQueryTest extends TestCase
+{
+    public function testEmptyByDefault(): void
+    {
+        $query = new SubQuery();
+
+        self::assertSame([], $query->tags);
+        self::assertSame([], $query->events);
+        self::assertSame(null, $query->streamName);
+        self::assertFalse($query->onlyLastEvent);
+
+        self::assertTrue($query->empty());
+    }
+
+    public function testNotEmpty(): void
+    {
+        $query = new SubQuery(['tag'], [ProfileCreated::class], 'foo', true);
+
+        self::assertFalse($query->empty());
+    }
+
+    #[DataProvider('providerForMatch')]
+    public function testMatch(SubQuery $subQuery, Message $message, bool $result): void
+    {
+        self::assertEquals($result, $subQuery->match($message));
+    }
+
+    /** @return Generator<string, array{SubQuery, Message, bool}> */
+    public static function providerForMatch(): Generator
+    {
+        yield 'match always with empty subquery' => [
+            new SubQuery(),
+            self::messageFactory(ProfileCreated::class, ['test'], 'foo'),
+            true,
+        ];
+
+        yield 'match always with empty subquery and only last event' => [
+            new SubQuery(onlyLastEvent: true),
+            self::messageFactory(ProfileCreated::class, ['test'], 'foo'),
+            true,
+        ];
+
+        yield 'match with perfect message' => [
+            new SubQuery(['test'], [ProfileCreated::class], 'foo'),
+            self::messageFactory(ProfileCreated::class, ['test'], 'foo'),
+            true,
+        ];
+
+        yield 'match with subset events' => [
+            new SubQuery(['test'], [ProfileCreated::class, ProfileVisited::class], 'foo'),
+            self::messageFactory(ProfileCreated::class, ['test'], 'foo'),
+            true,
+        ];
+
+        yield 'match with more tags on message' => [
+            new SubQuery(['test'], [ProfileCreated::class], 'foo'),
+            self::messageFactory(ProfileCreated::class, ['test', 'other'], 'foo'),
+            true,
+        ];
+
+        yield 'not match with wrong tag' => [
+            new SubQuery(['test'], [ProfileCreated::class], 'foo'),
+            self::messageFactory(ProfileCreated::class, ['other'], 'foo'),
+            false,
+        ];
+
+        yield 'not match with less tags on message' => [
+            new SubQuery(['test', 'other'], [ProfileCreated::class], 'foo'),
+            self::messageFactory(ProfileCreated::class, ['test'], 'foo'),
+            false,
+        ];
+
+        yield 'not match with wrong event' => [
+            new SubQuery(['test'], [ProfileCreated::class], 'foo'),
+            self::messageFactory(ProfileVisited::class, ['test'], 'foo'),
+            false,
+        ];
+
+        yield 'not match with wrong stream' => [
+            new SubQuery(['test'], [ProfileCreated::class], 'foo'),
+            self::messageFactory(ProfileCreated::class, ['test'], 'bar'),
+            false,
+        ];
+
+        yield 'not match with missing tag header' => [
+            new SubQuery(['test'], [ProfileCreated::class], 'foo'),
+            self::messageFactory(ProfileCreated::class, null, 'bar'),
+            false,
+        ];
+
+        yield 'not match with missing steam header' => [
+            new SubQuery(['test'], [ProfileCreated::class], 'foo'),
+            self::messageFactory(ProfileCreated::class, ['test']),
+            false,
+        ];
+    }
+
+    #[DataProvider('providerForIncludes')]
+    public function testIncludes(SubQuery $a, SubQuery $b, bool $result): void
+    {
+        self::assertEquals($result, $a->includes($b));
+    }
+
+    /** @return Generator<string, array{SubQuery, SubQuery, bool}> */
+    public static function providerForIncludes(): Generator
+    {
+        yield 'empty includes empty' => [
+            new SubQuery(),
+            new SubQuery(),
+            true,
+        ];
+
+        yield 'empty includes non-empty' => [
+            new SubQuery(),
+            new SubQuery(['tag']),
+            true,
+        ];
+
+        yield 'non-empty does not include empty' => [
+            new SubQuery(['tag']),
+            new SubQuery(),
+            false,
+        ];
+
+        yield 'same tags and events includes' => [
+            new SubQuery(['tag'], [ProfileCreated::class]),
+            new SubQuery(['tag'], [ProfileCreated::class]),
+            true,
+        ];
+
+        yield 'different tags does not include' => [
+            new SubQuery(['tag1'], [ProfileCreated::class]),
+            new SubQuery(['tag2'], [ProfileCreated::class]),
+            false,
+        ];
+
+        yield 'different events does not include' => [
+            new SubQuery(['tag'], [ProfileCreated::class]),
+            new SubQuery(['tag'], [ProfileVisited::class]),
+            false,
+        ];
+
+        yield 'subset includes' => [
+            new SubQuery(['tag1'], [ProfileCreated::class]),
+            new SubQuery(['tag1', 'tag2'], [ProfileCreated::class, ProfileVisited::class]),
+            true,
+        ];
+
+        yield 'non-subset not includes' => [
+            new SubQuery(['tag1', 'tag2'], [ProfileCreated::class, ProfileVisited::class]),
+            new SubQuery(['tag1'], [ProfileCreated::class]),
+            false,
+        ];
+
+        yield 'stream name equals includes' => [
+            new SubQuery(streamName: 'foo'),
+            new SubQuery(streamName: 'foo'),
+            true,
+        ];
+
+        yield 'stream name not equals does not include' => [
+            new SubQuery(streamName: 'foo'),
+            new SubQuery(streamName: 'bar'),
+            false,
+        ];
+
+        yield 'stream name does not include stream name not set' => [
+            new SubQuery(streamName: 'foo'),
+            new SubQuery(),
+            false,
+        ];
+
+        yield 'no stream name does include stream name set' => [
+            new SubQuery(),
+            new SubQuery(streamName: 'foo'),
+            true,
+        ];
+
+        yield 'only last event includes only last event' => [
+            new SubQuery(onlyLastEvent: true),
+            new SubQuery(onlyLastEvent: true),
+            true,
+        ];
+
+        yield 'only last event does not include only last event false' => [
+            new SubQuery(onlyLastEvent: true),
+            new SubQuery(onlyLastEvent: false),
+            false,
+        ];
+
+        yield 'only last event false does not include only last event true' => [
+            new SubQuery(onlyLastEvent: false),
+            new SubQuery(onlyLastEvent: true),
+            true,
+        ];
+    }
+
+    /**
+     * @param class-string      $class
+     * @param list<string>|null $tags
+     */
+    private static function messageFactory(string $class, array|null $tags = null, string|null $stream = null): Message
+    {
+        $message = match ($class) {
+            ProfileCreated::class => Message::create(new ProfileCreated(
+                ProfileId::fromString('1'),
+                Email::fromString('s'),
+            )),
+            ProfileVisited::class => Message::create(new ProfileVisited(ProfileId::fromString('1'))),
+            default => throw new InvalidArgumentException('unknown class'),
+        };
+
+        if ($tags !== null) {
+            $message = $message->withHeader(new TagsHeader($tags));
+        }
+
+        if ($stream !== null) {
+            $message = $message->withHeader(new StreamNameHeader($stream));
+        }
+
+        return $message;
+    }
+}

From e69b9b8ff76ac8039b09cf3c27f631bf5a362e4e Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Fri, 22 Aug 2025 09:19:03 +0200
Subject: [PATCH 19/22] replace trait with an abstract class

---
 docs/pages/dynamic_consistency_boundary.md    | 24 +++++++++----------
 .../{EventRouter.php => BasicProjection.php}  | 17 ++++++++-----
 src/DCB/CompositeProjection.php               | 20 +++++++++++-----
 src/DCB/Projection.php                        |  3 ---
 src/DCB/SubQueryProvider.php                  | 13 ++++++++++
 .../Projection/CourseCapacityProjection.php   |  7 ++----
 .../Course/Projection/CourseExists.php        |  9 +++----
 .../NumberOfCourseSubscriptionsProjection.php |  7 ++----
 ...NumberOfStudentSubscriptionsProjection.php |  7 ++----
 .../StudentAlreadySubscribedProjection.php    |  7 ++----
 .../NextInvoiceNumberProjection.php           |  7 ++----
 tests/Unit/Fixture/IncrementProjection.php    |  7 ++----
 12 files changed, 65 insertions(+), 63 deletions(-)
 rename src/DCB/{EventRouter.php => BasicProjection.php} (93%)
 create mode 100644 src/DCB/SubQueryProvider.php

diff --git a/docs/pages/dynamic_consistency_boundary.md b/docs/pages/dynamic_consistency_boundary.md
index 24194b96..bb0f94df 100644
--- a/docs/pages/dynamic_consistency_boundary.md
+++ b/docs/pages/dynamic_consistency_boundary.md
@@ -92,13 +92,13 @@ Course exists:
 
 ```php
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\EventRouter;
+use Patchlevel\EventSourcing\DCB\BasicProjection;
 use Patchlevel\EventSourcing\DCB\Projection;
 
 /** @implements Projection<bool> */
 final class CourseExists implements Projection
 {
-    use EventRouter;
+    use BasicProjection;
 
     public function __construct(private readonly CourseId $courseId) {}
 
@@ -125,12 +125,12 @@ Current capacity of a course:
 
 ```php
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\EventRouter;
+use Patchlevel\EventSourcing\DCB\BasicProjection;
 use Patchlevel\EventSourcing\DCB\Projection;
 
 final class CourseCapacityProjection implements Projection
 {
-    use EventRouter;
+    use BasicProjection;
 
     public function __construct(private readonly CourseId $courseId) {}
 
@@ -163,12 +163,12 @@ Count subscriptions of a course:
 
 ```php
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\EventRouter;
+use Patchlevel\EventSourcing\DCB\BasicProjection;
 use Patchlevel\EventSourcing\DCB\Projection;
 
 final class NumberOfCourseSubscriptionsProjection implements Projection
 {
-    use EventRouter;
+    use BasicProjection;
 
     public function __construct(private readonly CourseId $courseId) {}
 
@@ -195,12 +195,12 @@ Count subscriptions of a student:
 
 ```php
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\EventRouter;
+use Patchlevel\EventSourcing\DCB\BasicProjection;
 use Patchlevel\EventSourcing\DCB\Projection;
 
 final class NumberOfStudentSubscriptionsProjection implements Projection
 {
-    use EventRouter;
+    use BasicProjection;
 
     public function __construct(private readonly StudentId $studentId) {}
 
@@ -227,13 +227,13 @@ Has the student already subscribed to this course:
 
 ```php
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\EventRouter;
+use Patchlevel\EventSourcing\DCB\BasicProjection;
 use Patchlevel\EventSourcing\DCB\Projection;
 
 /** @implements Projection<bool> */
 final class StudentAlreadySubscribedProjection implements Projection
 {
-    use EventRouter;
+    use BasicProjection;
 
     public function __construct(
         private readonly StudentId $studentId,
@@ -266,12 +266,12 @@ Next invoice number from the last event only:
 
 ```php
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\EventRouter;
+use Patchlevel\EventSourcing\DCB\BasicProjection;
 use Patchlevel\EventSourcing\DCB\Projection;
 
 final class NextInvoiceNumberProjection implements Projection
 {
-    use EventRouter;
+    use BasicProjection;
 
     public function initialState(): int
     {
diff --git a/src/DCB/EventRouter.php b/src/DCB/BasicProjection.php
similarity index 93%
rename from src/DCB/EventRouter.php
rename to src/DCB/BasicProjection.php
index 46d198d5..cfec0db0 100644
--- a/src/DCB/EventRouter.php
+++ b/src/DCB/BasicProjection.php
@@ -21,14 +21,19 @@
 
 /**
  * @experimental
- * @require-implements Projection
  * @template S = mixed
+ * @implements Projection<S>
  */
-trait EventRouter
+abstract class BasicProjection implements Projection, SubQueryProvider
 {
     /** @var array<class-string, string>|null $applyMethods */
     private array|null $applyMethods = null;
 
+    /**
+     * @param S $state
+     *
+     * @return S
+     */
     public function apply(mixed $state, Message $message): mixed
     {
         if (!$this->subQuery()->match($message)) {
@@ -57,7 +62,7 @@ public function subQuery(): SubQuery
     }
 
     /** @return list<class-string> */
-    public function eventTypeFilter(): array
+    protected function eventTypeFilter(): array
     {
         return array_keys($this->applyMethods());
     }
@@ -177,14 +182,14 @@ static function (ReflectionNamedType|ReflectionIntersectionType $reflectionType)
     }
 
     /** @return list<string> */
-    abstract public function tagFilter(): array;
+    abstract protected function tagFilter(): array;
 
-    public function streamName(): string|null
+    protected function streamName(): string|null
     {
         return null;
     }
 
-    public function lastEventIsEnough(): bool
+    protected function lastEventIsEnough(): bool
     {
         return false;
     }
diff --git a/src/DCB/CompositeProjection.php b/src/DCB/CompositeProjection.php
index 5976c390..cabb0ea0 100644
--- a/src/DCB/CompositeProjection.php
+++ b/src/DCB/CompositeProjection.php
@@ -6,6 +6,7 @@
 
 use Patchlevel\EventSourcing\Message\Message;
 use Patchlevel\EventSourcing\Store\Query;
+use Patchlevel\EventSourcing\Store\SubQuery;
 
 use function array_map;
 
@@ -20,12 +21,19 @@ public function __construct(
 
     public function query(): Query
     {
-        $query = new Query(
-            ...array_map(
-                static fn (Projection $projection) => $projection->subQuery(),
-                $this->projections,
-            ),
-        );
+        $subQueries = [];
+
+        foreach ($this->projections as $projection) {
+            if ($projection instanceof SubQueryProvider) {
+                $subQueries[] = $projection->subQuery();
+
+                continue;
+            }
+
+            $subQueries[] = new SubQuery();
+        }
+
+        $query = new Query(...$subQueries);
 
         return $query->optimize();
     }
diff --git a/src/DCB/Projection.php b/src/DCB/Projection.php
index 67aeb3c4..47c709be 100644
--- a/src/DCB/Projection.php
+++ b/src/DCB/Projection.php
@@ -5,7 +5,6 @@
 namespace Patchlevel\EventSourcing\DCB;
 
 use Patchlevel\EventSourcing\Message\Message;
-use Patchlevel\EventSourcing\Store\SubQuery;
 
 /**
  * @experimental
@@ -22,6 +21,4 @@ public function initialState(): mixed;
      * @return S
      */
     public function apply(mixed $state, Message $message): mixed;
-
-    public function subQuery(): SubQuery;
 }
diff --git a/src/DCB/SubQueryProvider.php b/src/DCB/SubQueryProvider.php
new file mode 100644
index 00000000..0fbcd596
--- /dev/null
+++ b/src/DCB/SubQueryProvider.php
@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\DCB;
+
+use Patchlevel\EventSourcing\Store\SubQuery;
+
+/** @experimental */
+interface SubQueryProvider
+{
+    public function subQuery(): SubQuery;
+}
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php
index b7644667..fe8efab2 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseCapacityProjection.php
@@ -5,16 +5,13 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\EventRouter;
-use Patchlevel\EventSourcing\DCB\Projection;
+use Patchlevel\EventSourcing\DCB\BasicProjection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseCapacityChanged;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseDefined;
 
-final class CourseCapacityProjection implements Projection
+final class CourseCapacityProjection extends BasicProjection
 {
-    use EventRouter;
-
     public function __construct(
         private readonly CourseId $courseId,
     ) {
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php
index 7523df05..64317696 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/CourseExists.php
@@ -5,16 +5,13 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\EventRouter;
-use Patchlevel\EventSourcing\DCB\Projection;
+use Patchlevel\EventSourcing\DCB\BasicProjection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\CourseDefined;
 
-/** @implements Projection<bool> */
-final class CourseExists implements Projection
+/** @extends BasicProjection<bool> */
+final class CourseExists extends BasicProjection
 {
-    use EventRouter;
-
     public function __construct(
         private readonly CourseId $courseId,
     ) {
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php
index 88c48c82..3022448f 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfCourseSubscriptionsProjection.php
@@ -5,15 +5,12 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\EventRouter;
-use Patchlevel\EventSourcing\DCB\Projection;
+use Patchlevel\EventSourcing\DCB\BasicProjection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\StudentSubscribedToCourse;
 
-final class NumberOfCourseSubscriptionsProjection implements Projection
+final class NumberOfCourseSubscriptionsProjection extends BasicProjection
 {
-    use EventRouter;
-
     public function __construct(
         private readonly CourseId $courseId,
     ) {
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php
index a3045d09..c6a2a41e 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/NumberOfStudentSubscriptionsProjection.php
@@ -5,15 +5,12 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\EventRouter;
-use Patchlevel\EventSourcing\DCB\Projection;
+use Patchlevel\EventSourcing\DCB\BasicProjection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\StudentSubscribedToCourse;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\StudentId;
 
-final class NumberOfStudentSubscriptionsProjection implements Projection
+final class NumberOfStudentSubscriptionsProjection extends BasicProjection
 {
-    use EventRouter;
-
     public function __construct(
         private readonly StudentId $studentId,
     ) {
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php
index 83673d00..c642fbfc 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/Projection/StudentAlreadySubscribedProjection.php
@@ -5,16 +5,13 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\EventRouter;
-use Patchlevel\EventSourcing\DCB\Projection;
+use Patchlevel\EventSourcing\DCB\BasicProjection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\CourseId;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\Event\StudentSubscribedToCourse;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course\StudentId;
 
-final class StudentAlreadySubscribedProjection implements Projection
+final class StudentAlreadySubscribedProjection extends BasicProjection
 {
-    use EventRouter;
-
     public function __construct(
         private readonly StudentId $studentId,
         private readonly CourseId $courseId,
diff --git a/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php b/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
index 5cfb7c88..1daf3396 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Invoice/Projection/NextInvoiceNumberProjection.php
@@ -5,14 +5,11 @@
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Projection;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\EventRouter;
-use Patchlevel\EventSourcing\DCB\Projection;
+use Patchlevel\EventSourcing\DCB\BasicProjection;
 use Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Invoice\Event\InvoiceCreated;
 
-final class NextInvoiceNumberProjection implements Projection
+final class NextInvoiceNumberProjection extends BasicProjection
 {
-    use EventRouter;
-
     /** @return list<string> */
     public function tagFilter(): array
     {
diff --git a/tests/Unit/Fixture/IncrementProjection.php b/tests/Unit/Fixture/IncrementProjection.php
index ced2180d..afdc80c0 100644
--- a/tests/Unit/Fixture/IncrementProjection.php
+++ b/tests/Unit/Fixture/IncrementProjection.php
@@ -5,13 +5,10 @@
 namespace Patchlevel\EventSourcing\Tests\Unit\Fixture;
 
 use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\EventRouter;
-use Patchlevel\EventSourcing\DCB\Projection;
+use Patchlevel\EventSourcing\DCB\BasicProjection;
 
-final class IncrementProjection implements Projection
+final class IncrementProjection extends BasicProjection
 {
-    use EventRouter;
-
     /** @param list<string> $tags */
     public function __construct(
         private readonly int $initial,

From 1c067cfaf880242d672d60195e1beee135baf035 Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Fri, 22 Aug 2025 12:33:39 +0200
Subject: [PATCH 20/22] update documentation

---
 docs/pages/dynamic_consistency_boundary.md | 109 +++++++++------------
 1 file changed, 45 insertions(+), 64 deletions(-)

diff --git a/docs/pages/dynamic_consistency_boundary.md b/docs/pages/dynamic_consistency_boundary.md
index bb0f94df..d03fb3d6 100644
--- a/docs/pages/dynamic_consistency_boundary.md
+++ b/docs/pages/dynamic_consistency_boundary.md
@@ -1,85 +1,83 @@
 # Dynamic Consistency Boundary
 
-In our little DCB getting-started example, we decide things atomically across multiple event streams without loading aggregates.
-We keep the example small and show how to validate a course subscription and how to generate invoice numbers using the DCB API.
+??? example "Experimental"
+
+    This feature is still experimental and may change in the future.
+    Use it with caution.
+
+Dynamic Consistency Boundary (DCB) is an event‑sourcing approach for making consistent, 
+cross‑stream decisions without loading full aggregates. 
+For each decision, it builds a minimal, purpose‑built state from a targeted subset of events selected via tags. 
+Lightweight projections compute just the values needed to validate commands and derive new events. 
+The decision evaluation and event append are coupled by an optimistic append condition to prevent race conditions; 
+if the queried subset changes concurrently, the write is rejected and can be retried. 
+This makes handlers simple, fast, and scalable, since only relevant events are processed. 
+DCB is a great fit when business rules span multiple streams.
 
 !!! note
 
-    DCB is marked as experimental. APIs may change.
+    You can read more about Dynamic Consistency Boundary on page [dcb.events](https://dcb.events/).
+
+Since this approach differs slightly from the standard "aggregate" event sourcing principle, 
+we will use the [Getting Started](./getting_started.md) example and build it as a DCB variant.
+
+In our litt le getting started example, we manage hotels.
+We keep the example small, so we can only create hotels and let guests check in and check out.
 
 ## Define some events
 
 First we define the events that happen in our system.
 
-A course can be defined with a capacity:
+A hotel can be created with a `name` and a `id`:
 
 ```php
+use Patchlevel\EventSourcing\Aggregate\Uuid;
 use Patchlevel\EventSourcing\Attribute\Event;
 use Patchlevel\EventSourcing\Attribute\EventTag;
 
-#[Event('course.defined')]
-final class CourseDefined
+#[Event('hotel.created')]
+final class HotelCreated
 {
     public function __construct(
-        #[EventTag(prefix: 'course')]
-        public CourseId $courseId,
-        public int $capacity,
+        #[EventTag(prefix: 'hotel')]
+        public readonly Uuid $hotelId,
+        public readonly string $hotelName,
     ) {
     }
 }
 ```
-A course capacity can change later:
+A guest can check in by `name`:
 
 ```php
 use Patchlevel\EventSourcing\Attribute\Event;
-use Patchlevel\EventSourcing\Attribute\EventTag;
 
-#[Event('course.capacity_changed')]
-final class CourseCapacityChanged
+#[Event('hotel.guest_checked_in')]
+final class GuestIsCheckedIn
 {
     public function __construct(
-        #[EventTag(prefix: 'course')]
-        public CourseId $courseId,
-        public int $capacity,
+        public readonly string $guestName,
     ) {
     }
 }
 ```
-A student can subscribe to a course. We tag the event with both student and course, so that DCB projections can select the exact subset of events:
+And also check out again:
 
 ```php
 use Patchlevel\EventSourcing\Attribute\Event;
-use Patchlevel\EventSourcing\Attribute\EventTag;
 
-#[Event('course.student_subscribed')]
-final class StudentSubscribedToCourse
+#[Event('hotel.guest_checked_out')]
+final class GuestIsCheckedOut
 {
     public function __construct(
-        #[EventTag(prefix: 'student')]
-        public readonly StudentId $studentId,
-        #[EventTag(prefix: 'course')]
-        public readonly CourseId $courseId,
+        public readonly string $guestName,
     ) {
     }
 }
 ```
-And finally, an invoice can be created with a monotonically increasing number:
+!!! note
 
-```php
-use Patchlevel\EventSourcing\Attribute\Event;
-use Patchlevel\EventSourcing\Attribute\EventTag;
+    You can find out more about events [here](events.md).    
 
-#[Event('invoice.created')]
-final class InvoiceCreated
-{
-    public function __construct(
-        #[EventTag(prefix: 'invoice')]
-        public readonly int $invoiceNumber,
-        public readonly int $money,
-    ) {
-    }
-}
-```
 
 ## Define projections
 
@@ -93,13 +91,10 @@ Course exists:
 ```php
 use Patchlevel\EventSourcing\Attribute\Apply;
 use Patchlevel\EventSourcing\DCB\BasicProjection;
-use Patchlevel\EventSourcing\DCB\Projection;
 
-/** @implements Projection<bool> */
-final class CourseExists implements Projection
+/** @extends BasicProjection<bool> */
+final class CourseExists extends BasicProjection
 {
-    use BasicProjection;
-
     public function __construct(private readonly CourseId $courseId) {}
 
     public function initialState(): bool
@@ -126,12 +121,9 @@ Current capacity of a course:
 ```php
 use Patchlevel\EventSourcing\Attribute\Apply;
 use Patchlevel\EventSourcing\DCB\BasicProjection;
-use Patchlevel\EventSourcing\DCB\Projection;
 
-final class CourseCapacityProjection implements Projection
+final class CourseCapacityProjection extends BasicProjection
 {
-    use BasicProjection;
-
     public function __construct(private readonly CourseId $courseId) {}
 
     public function initialState(): int
@@ -164,12 +156,9 @@ Count subscriptions of a course:
 ```php
 use Patchlevel\EventSourcing\Attribute\Apply;
 use Patchlevel\EventSourcing\DCB\BasicProjection;
-use Patchlevel\EventSourcing\DCB\Projection;
 
-final class NumberOfCourseSubscriptionsProjection implements Projection
+final class NumberOfCourseSubscriptionsProjection extends BasicProjection
 {
-    use BasicProjection;
-
     public function __construct(private readonly CourseId $courseId) {}
 
     public function initialState(): int
@@ -198,10 +187,8 @@ use Patchlevel\EventSourcing\Attribute\Apply;
 use Patchlevel\EventSourcing\DCB\BasicProjection;
 use Patchlevel\EventSourcing\DCB\Projection;
 
-final class NumberOfStudentSubscriptionsProjection implements Projection
+final class NumberOfStudentSubscriptionsProjection extends BasicProjection
 {
-    use BasicProjection;
-
     public function __construct(private readonly StudentId $studentId) {}
 
     public function initialState(): int
@@ -228,13 +215,10 @@ Has the student already subscribed to this course:
 ```php
 use Patchlevel\EventSourcing\Attribute\Apply;
 use Patchlevel\EventSourcing\DCB\BasicProjection;
-use Patchlevel\EventSourcing\DCB\Projection;
 
-/** @implements Projection<bool> */
-final class StudentAlreadySubscribedProjection implements Projection
+/** @extends  BasicProjection<bool> */
+final class StudentAlreadySubscribedProjection extends BasicProjection
 {
-    use BasicProjection;
-
     public function __construct(
         private readonly StudentId $studentId,
         private readonly CourseId $courseId,
@@ -267,12 +251,9 @@ Next invoice number from the last event only:
 ```php
 use Patchlevel\EventSourcing\Attribute\Apply;
 use Patchlevel\EventSourcing\DCB\BasicProjection;
-use Patchlevel\EventSourcing\DCB\Projection;
 
-final class NextInvoiceNumberProjection implements Projection
+final class NextInvoiceNumberProjection extends BasicProjection
 {
-    use BasicProjection;
-
     public function initialState(): int
     {
         return 1;

From 666e2bbe6518a2e4fc6453c2d7855b5b4eb0d13d Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Fri, 22 Aug 2025 15:50:36 +0200
Subject: [PATCH 21/22] update docs

---
 docs/pages/dynamic_consistency_boundary.md | 410 +++++++++------------
 phpstan-baseline.neon                      |   6 -
 2 files changed, 175 insertions(+), 241 deletions(-)

diff --git a/docs/pages/dynamic_consistency_boundary.md b/docs/pages/dynamic_consistency_boundary.md
index d03fb3d6..78d0d282 100644
--- a/docs/pages/dynamic_consistency_boundary.md
+++ b/docs/pages/dynamic_consistency_boundary.md
@@ -21,14 +21,14 @@ DCB is a great fit when business rules span multiple streams.
 Since this approach differs slightly from the standard "aggregate" event sourcing principle, 
 we will use the [Getting Started](./getting_started.md) example and build it as a DCB variant.
 
-In our litt le getting started example, we manage hotels.
+In our little getting started example, we manage hotels.
 We keep the example small, so we can only create hotels and let guests check in and check out.
 
 ## Define some events
 
 First we define the events that happen in our system.
 
-A hotel can be created with a `name` and a `id`:
+A hotel can be created with an ID and a name. In DCB we also tag the hotelId so projections can filter by this hotel.
 
 ```php
 use Patchlevel\EventSourcing\Aggregate\Uuid;
@@ -46,248 +46,226 @@ final class HotelCreated
     }
 }
 ```
-A guest can check in by `name`:
+
+A guest can check in. 
+We tag the hotelId and the guest name so projections can filter by this combination.
 
 ```php
+use Patchlevel\EventSourcing\Aggregate\Uuid;
 use Patchlevel\EventSourcing\Attribute\Event;
+use Patchlevel\EventSourcing\Attribute\EventTag;
 
 #[Event('hotel.guest_checked_in')]
 final class GuestIsCheckedIn
 {
     public function __construct(
+        #[EventTag(prefix: 'hotel')]
+        public readonly Uuid $hotelId,
+        #[EventTag(prefix: 'guest')]
         public readonly string $guestName,
     ) {
     }
 }
 ```
-And also check out again:
+
+A guest can check out again. Here we tag the hotelId and the guest name again.
 
 ```php
+use Patchlevel\EventSourcing\Aggregate\Uuid;
 use Patchlevel\EventSourcing\Attribute\Event;
+use Patchlevel\EventSourcing\Attribute\EventTag;
 
 #[Event('hotel.guest_checked_out')]
 final class GuestIsCheckedOut
 {
     public function __construct(
+        #[EventTag(prefix: 'hotel')]
+        public readonly Uuid $hotelId,
+        #[EventTag(prefix: 'guest')]
         public readonly string $guestName,
     ) {
     }
 }
 ```
+
 !!! note
 
     You can find out more about events [here](events.md).    
 
+## Define Commands
 
-## Define projections
-
-DCB builds a tiny, purpose-built state just for the current decision using projections.
-A projection selects events via tags, processes those events and yields a small value.
-
-We use the EventRouter trait which wires `#[Apply]` methods and builds a SubQuery from filters.
+Unlike in the [Getting Started](./getting_started.md) section, we're working with the [Command Bus](./command_bus.md) here. 
+This allows us to express our interaction with the system using commands. We can do the following with our system:
 
-Course exists:
+The following command creates a new hotel. It carries the hotel ID and name.
 
 ```php
-use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\BasicProjection;
-
-/** @extends BasicProjection<bool> */
-final class CourseExists extends BasicProjection
-{
-    public function __construct(private readonly CourseId $courseId) {}
+class CreateHotel {
+    public function __construct(
+        public HotelId $hotelId,
+        public readonly string $hotelName,
+   ) {    
+   }
+}
+```
 
-    public function initialState(): bool
-    {
-        return false;
-    }
+Next, this command checks a guest in to a specific hotel.
+It contains the hotel ID and the guest name.
 
-    /** @return list<string> */
-    public function tagFilter(): array
-    {
-        return ["course:{$this->courseId->toString()}"];
-    }
-
-    #[Apply]
-    public function applyCourseDefined(bool $state, CourseDefined $event): bool
-    {
-        return true;
-    }
+```php
+class CheckIn {
+    public function __construct(
+        public HotelId $hotelId,
+        public readonly string $guestName,
+   ) {    
+   }
 }
 ```
 
-Current capacity of a course:
+Last but not least, this command checks a guest out of a specific hotel.
+It also provides the hotel ID and guest name.
 
 ```php
-use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\BasicProjection;
+class CheckOut {
+    public function __construct(
+        public HotelId $hotelId,
+        public readonly string $guestName,
+   ) {    
+   }
+}
+```
 
-final class CourseCapacityProjection extends BasicProjection
-{
-    public function __construct(private readonly CourseId $courseId) {}
+## Define projections
 
-    public function initialState(): int
-    {
-        return 0;
-    }
+With DCB we don’t load an aggregate. 
+Instead, we assemble the minimal state for a single decision from lightweight projections. 
 
-    /** @return list<string> */
-    public function tagFilter(): array
-    {
-        return ["course:{$this->courseId->toString()}"];
-    }
+Each projection:
 
-    #[Apply]
-    public function applyCourseDefined(int $state, CourseDefined $event): int
-    {
-        return $event->capacity;
-    }
+* Declares an initial state
+* Applies only the few events relevant to compute the decision value
+* Optionally filters events by tags
 
-    #[Apply]
-    public function applyCourseCapacityChanged(int $state, CourseCapacityChanged $event): int
-    {
-        return $event->capacity;
-    }
-}
-```
-
-Count subscriptions of a course:
+The first projection answers only whether the hotel already exists.
 
 ```php
 use Patchlevel\EventSourcing\Attribute\Apply;
 use Patchlevel\EventSourcing\DCB\BasicProjection;
 
-final class NumberOfCourseSubscriptionsProjection extends BasicProjection
+final class HotelExists extends BasicProjection
 {
-    public function __construct(private readonly CourseId $courseId) {}
+    public function __construct(
+        private readonly Uuid $hotelId
+    ) {
+    }
 
-    public function initialState(): int
-    {
-        return 0;
+    public function initialState(): bool 
+    { 
+        return false; 
     }
 
     /** @return list<string> */
-    public function tagFilter(): array
+    protected function tagFilter(): array
     {
-        return ["course:{$this->courseId->toString()}"];
+        return ["hotel:{$this->hotelId->toString()}"];
     }
 
     #[Apply]
-    public function applyStudentSubscribedToCourse(int $state, StudentSubscribedToCourse $event): int
+    public function applyHotelCreated(bool $state, HotelCreated $event): bool
     {
-        return $state + 1;
+        return true;
     }
 }
 ```
 
-Count subscriptions of a student:
+The second projection counts the guests currently checked in.
 
 ```php
 use Patchlevel\EventSourcing\Attribute\Apply;
 use Patchlevel\EventSourcing\DCB\BasicProjection;
-use Patchlevel\EventSourcing\DCB\Projection;
 
-final class NumberOfStudentSubscriptionsProjection extends BasicProjection
+final class NumberOfGuestsInHotel extends BasicProjection
 {
-    public function __construct(private readonly StudentId $studentId) {}
+    public function __construct(
+        private readonly Uuid $hotelId
+    ) {
+    }
 
-    public function initialState(): int
-    {
-        return 0;
+    public function initialState(): int 
+    { 
+        return 0; 
     }
 
     /** @return list<string> */
-    public function tagFilter(): array
+    protected function tagFilter(): array
     {
-        return ["student:{$this->studentId->toString()}"];
+        return ["hotel:{$this->hotelId->toString()}"]; // same tag as above
     }
 
     #[Apply]
-    public function applyStudentSubscribedToCourse(int $state, StudentSubscribedToCourse $event): int
+    public function applyGuestIsCheckedIn(int $state, GuestIsCheckedIn $event): int
     {
         return $state + 1;
     }
+
+    #[Apply]
+    public function applyGuestIsCheckedOut(int $state, GuestIsCheckedOut $event): int
+    {
+        return $state - 1;
+    }
 }
 ```
 
-Has the student already subscribed to this course:
+The third projection answers whether the given guest is already checked into this hotel.
 
 ```php
 use Patchlevel\EventSourcing\Attribute\Apply;
 use Patchlevel\EventSourcing\DCB\BasicProjection;
 
-/** @extends  BasicProjection<bool> */
-final class StudentAlreadySubscribedProjection extends BasicProjection
+final class GuestAlreadyCheckedIn extends BasicProjection
 {
     public function __construct(
-        private readonly StudentId $studentId,
-        private readonly CourseId $courseId,
+        private readonly Uuid $hotelId,
+        private readonly string $guestName,
     ) {}
 
-    public function initialState(): bool
-    {
-        return false;
-    }
+    public function initialState(): bool { return false; }
 
     /** @return list<string> */
-    public function tagFilter(): array
+    protected function tagFilter(): array
     {
         return [
-            "student:{$this->studentId->toString()}",
-            "course:{$this->courseId->toString()}",
+            "hotel:{$this->hotelId->toString()}",
+            "guest:{$this->guestName}",
         ];
     }
 
     #[Apply]
-    public function applyStudentSubscribedToCourse(bool $state, StudentSubscribedToCourse $event): bool
+    public function applyGuestIsCheckedIn(bool $state, GuestIsCheckedIn $event): bool
     {
         return true;
     }
-}
-```
-
-Next invoice number from the last event only:
-
-```php
-use Patchlevel\EventSourcing\Attribute\Apply;
-use Patchlevel\EventSourcing\DCB\BasicProjection;
-
-final class NextInvoiceNumberProjection extends BasicProjection
-{
-    public function initialState(): int
-    {
-        return 1;
-    }
 
     #[Apply]
-    public function applyInvoiceCreated(int $state, InvoiceCreated $event): int
+    public function applyGuestIsCheckedOut(bool $state, GuestIsCheckedOut $event): bool
     {
-        return $event->invoiceNumber + 1;
-    }
-
-    public function lastEventIsEnough(): bool
-    {
-        return true; // optimize: only the last matching event is needed
+        return false;
     }
 }
 ```
 
-!!! tip
-
-    `#[Apply]` methods can be named freely. The second parameter’s type determines which event is routed.
+## Define handlers
 
-## Write handlers
+We’ll implement three command handlers corresponding to our commands.
 
-Now we can build decisions and append new events atomically by using the DecisionModelBuilder and EventAppender.
-
-Define a course only if it does not exist yet:
+First, we implement the handler for the `CreateHotel` command.
 
 ```php
 use Patchlevel\EventSourcing\Attribute\Handle;
 use Patchlevel\EventSourcing\DCB\DecisionModelBuilder;
 use Patchlevel\EventSourcing\DCB\EventAppender;
 
-final class DefineCourseHandler
+final class CreateHotelHandler
 {
     public function __construct(
         private readonly DecisionModelBuilder $decisionModelBuilder,
@@ -295,68 +273,36 @@ final class DefineCourseHandler
     ) {}
 
     #[Handle]
-    public function __invoke(DefineCourse $command): void
+    public function __invoke(CreateHotel $command): void
     {
         $state = $this->decisionModelBuilder->build([
-            'courseExists' => new CourseExists($command->courseId),
+            'hotelExists' => new HotelExists($command->hotelId),
         ]);
 
-        if ($state['courseExists']) {
-            throw new RuntimeException('Course already exists');
+        if ($state['hotelExists']) {
+            throw new RuntimeException('Hotel already exists');
         }
 
         $this->eventAppender->append([
-            new CourseDefined($command->courseId, $command->capacity),
+            new HotelCreated($command->hotelId, $command->hotelName),
         ], $state->appendCondition);
     }
 }
 ```
 
-Change capacity if different:
-
-```php
-use Patchlevel\EventSourcing\Attribute\Handle;
-use Patchlevel\EventSourcing\DCB\DecisionModelBuilder;
-use Patchlevel\EventSourcing\DCB\EventAppender;
-
-final class ChangeCourseCapacityHandler
-{
-    public function __construct(
-        private readonly DecisionModelBuilder $decisionModelBuilder,
-        private readonly EventAppender $eventAppender,
-    ) {}
-
-    #[Handle]
-    public function __invoke(ChangeCourseCapacity $command): void
-    {
-        $state = $this->decisionModelBuilder->build([
-            'courseExists' => new CourseExists($command->courseId),
-            'courseCapacity' => new CourseCapacityProjection($command->courseId),
-        ]);
+!!! note
 
-        if (!$state['courseExists']) {
-            throw new RuntimeException('Course does not exist');
-        }
+    Handlers build a Decision Model from the projections and then append events with an optimistic AppendCondition. 
+    If any relevant event arrives between read and write, the append fails and you can retry.
 
-        if ($state['courseCapacity'] === $command->capacity) {
-            return;
-        }
-
-        $this->eventAppender->append([
-            new CourseCapacityChanged($command->courseId, $command->capacity),
-        ], $state->appendCondition);
-    }
-}
-```
-
-Subscribe a student with multiple checks atomically:
+The next handler implements the `CheckIn` command.
 
 ```php
 use Patchlevel\EventSourcing\Attribute\Handle;
 use Patchlevel\EventSourcing\DCB\DecisionModelBuilder;
 use Patchlevel\EventSourcing\DCB\EventAppender;
 
-final class SubscribeStudentToCourseHandler
+final class CheckInHandler
 {
     public function __construct(
         private readonly DecisionModelBuilder $decisionModelBuilder,
@@ -364,47 +310,42 @@ final class SubscribeStudentToCourseHandler
     ) {}
 
     #[Handle]
-    public function __invoke(SubscribeStudentToCourse $command): void
+    public function __invoke(CheckIn $command): void
     {
         $state = $this->decisionModelBuilder->build([
-            'courseExists' => new CourseExists($command->courseId),
-            'courseCapacity' => new CourseCapacityProjection($command->courseId),
-            'numberOfCourseSubscriptions' => new NumberOfCourseSubscriptionsProjection($command->courseId),
-            'numberOfStudentSubscriptions' => new NumberOfStudentSubscriptionsProjection($command->studentId),
-            'studentAlreadySubscribed' => new StudentAlreadySubscribedProjection($command->studentId, $command->courseId),
+            'hotelExists' => new HotelExists($command->hotelId),
+            'guestCount' => new NumberOfGuestsInHotel($command->hotelId),
+            'alreadyIn' => new GuestAlreadyCheckedIn($command->hotelId, $command->guestName),
         ]);
 
-        if (!$state['courseExists']) {
-            throw new RuntimeException("Course {$command->courseId->toString()} does not exist");
+        if (!$state['hotelExists']) {
+            throw new RuntimeException('Hotel does not exist');
         }
 
-        if ($state['numberOfCourseSubscriptions'] >= $state['courseCapacity']) {
-            throw new RuntimeException("Course {$command->courseId->toString()} is not available");
+        if ($state['alreadyIn']) {
+            throw new RuntimeException(sprintf('Guest "%s" already checked in', $command->guestName));
         }
 
-        if ($state['studentAlreadySubscribed']) {
-            throw new RuntimeException("Student {$command->studentId->toString()} is already subscribed to course {$command->courseId->toString()}");
-        }
-
-        if ($state['numberOfStudentSubscriptions'] >= 5) {
-            throw new RuntimeException("Student {$command->studentId->toString()} is already subscribed to 5 courses");
+        // Optional policy example: max 5 guests
+        if ($state['guestCount'] >= 5) {
+            throw new RuntimeException('Hotel is full');
         }
 
         $this->eventAppender->append([
-            new StudentSubscribedToCourse($command->studentId, $command->courseId),
+            new GuestIsCheckedIn($command->hotelId, $command->guestName),
         ], $state->appendCondition);
     }
 }
 ```
 
-Create invoices while safely generating the next number from the last event only:
+And the last handler implements the `CheckOut` command.
 
 ```php
 use Patchlevel\EventSourcing\Attribute\Handle;
 use Patchlevel\EventSourcing\DCB\DecisionModelBuilder;
 use Patchlevel\EventSourcing\DCB\EventAppender;
 
-final class CreateInvoiceHandler
+final class CheckOutHandler
 {
     public function __construct(
         private readonly DecisionModelBuilder $decisionModelBuilder,
@@ -412,99 +353,98 @@ final class CreateInvoiceHandler
     ) {}
 
     #[Handle]
-    public function __invoke(CreateInvoice $command): void
+    public function __invoke(CheckOut $command): void
     {
         $state = $this->decisionModelBuilder->build([
-            'nextInvoiceNumber' => new NextInvoiceNumberProjection(),
+            'hotelExists' => new HotelExists($command->hotelId),
+            'alreadyIn' => new GuestAlreadyCheckedIn($command->hotelId, $command->guestName),
         ]);
 
+        if (!$state['hotelExists']) {
+            throw new RuntimeException('Hotel does not exist');
+        }
+
+        if (!$state['alreadyIn']) {
+            throw new RuntimeException(sprintf('Guest "%s" is not checked in', $command->guestName));
+        }
+
         $this->eventAppender->append([
-            new InvoiceCreated($state['nextInvoiceNumber'], $command->money),
+            new GuestIsCheckedOut($command->hotelId, $command->guestName),
         ], $state->appendCondition);
     }
 }
 ```
 
-!!! tip
-
-    If any concurrent writer changes the queried subset in between build() and append(), the store will reject the write (optimistic concurrency). You can retry if appropriate.
-
 ## Configuration
 
-Now we plug the whole thing together. We use the TaggableDoctrineDbalStore plus the DCB builder and appender.
+Now we can wire everything together.
 
 ```php
+use Doctrine\DBAL\DriverManager;
+use Doctrine\DBAL\Tools\DsnParser;
 use Patchlevel\EventSourcing\CommandBus\ServiceHandlerProvider;
 use Patchlevel\EventSourcing\CommandBus\SyncCommandBus;
 use Patchlevel\EventSourcing\DCB\StoreDecisionModelBuilder;
 use Patchlevel\EventSourcing\DCB\StoreEventAppender;
-use Patchlevel\EventSourcing\Metadata\Event\AttributeEventRegistryFactory;
 use Patchlevel\EventSourcing\Serializer\DefaultEventSerializer;
 use Patchlevel\EventSourcing\Store\TaggableDoctrineDbalStore;
 
-$store = new TaggableDoctrineDbalStore(
-    $connection,
-    DefaultEventSerializer::createFromPaths([__DIR__ . '/Event']),
-    (new AttributeEventRegistryFactory())->create([__DIR__ . '/Event']),
-);
+$connection = DriverManager::getConnection((new DsnParser())->parse('pdo-pgsql://user:secret@localhost/app'));
+$serializer = DefaultEventSerializer::createFromPaths(['src/Domain/Hotel/Event']);
 
-$decisionModelBuilder = new StoreDecisionModelBuilder($store);
-$eventAppender = new StoreEventAppender($store);
+$eventStore = new TaggableDoctrineDbalStore($connection, $serializer, $eventRegistry);
 
-$commandBus = new SyncCommandBus(
-    new ServiceHandlerProvider([
-        new DefineCourseHandler($decisionModelBuilder, $eventAppender),
-        new ChangeCourseCapacityHandler($decisionModelBuilder, $eventAppender),
-        new SubscribeStudentToCourseHandler($decisionModelBuilder, $eventAppender),
-        new CreateInvoiceHandler($decisionModelBuilder, $eventAppender),
-    ]),
-);
+$decisionModelBuilder = new StoreDecisionModelBuilder($eventStore);
+$eventAppender = new StoreEventAppender($eventStore);
+
+$provider = new ServiceHandlerProvider([
+    new CreateHotelHandler($decisionModelBuilder, $eventAppender),
+    new CheckInHandler($decisionModelBuilder, $eventAppender),
+    new CheckOutHandler($decisionModelBuilder, $eventAppender),
+]);
+
+$commandBus = new SyncCommandBus($provider);
 ```
 
 ## Database setup
 
-To actually write data to the database we need to create the event table.
+The last step is to create the database schema.
 
 ```php
 use Patchlevel\EventSourcing\Schema\DoctrineSchemaDirector;
+use Patchlevel\EventSourcing\Schema\ChainDoctrineSchemaConfigurator;
+use Patchlevel\EventSourcing\Store\Store;
 
-$schemaDirector = new DoctrineSchemaDirector($connection, $store);
+$schemaDirector = new DoctrineSchemaDirector(
+    $connection,
+    new ChainDoctrineSchemaConfigurator([$eventStore]),
+);
 $schemaDirector->create();
 ```
 
-!!! note
-
-    You can also use the predefined CLI commands to create and drop the schema. See the CLI documentation.
-
 ## Usage
 
-We are now ready to use DCB. We can dispatch commands and DCB will keep each decision consistent.
+Now we can use our command bus to execute our commands.
 
 ```php
-$courseId = CourseId::generate();
-$student1 = StudentId::generate();
-$student2 = StudentId::generate();
-
-$commandBus->dispatch(new DefineCourse($courseId, 10));
-$commandBus->dispatch(new ChangeCourseCapacity($courseId, 2));
-$commandBus->dispatch(new SubscribeStudentToCourse($student1, $courseId));
-$commandBus->dispatch(new SubscribeStudentToCourse($student2, $courseId));
+use Patchlevel\EventSourcing\Aggregate\Uuid;
 
-$commandBus->dispatch(new CreateInvoice(10));
-$commandBus->dispatch(new CreateInvoice(10));
+$hotelId = Uuid::generate();
+$commandBus->dispatch(new CreateHotel($hotelId, 'HOTEL'));
+$commandBus->dispatch(new CheckIn($hotelId, 'David'));
+$commandBus->dispatch(new CheckIn($hotelId, 'Daniel'));
+$commandBus->dispatch(new CheckOut($hotelId, 'David'));
 ```
 
-## Result
-
-!!! success
+## Conclusion
 
-    We have successfully implemented and used DCB to make consistent decisions across multiple streams without loading aggregates.
-    Feel free to browse further in the documentation for more detailed information.
+We've seen how to use DCB to make decisions consistently.
+In this example we skipped the subscription part,
+but you can add it by following the [Getting Started](./getting_started.md) section.
 
 ## Learn more
 
-* [How to use command bus](command_bus.md)
-* [How to use aggregates](aggregate.md)
-* [How to use aggregate id](aggregate_id.md)
-* [How to use clock](clock.md)
+* [Events](./events.md)
+* [Command Bus](./command_bus.md)
+* [Store](./store.md)
 
diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index 3aea54d9..83635f14 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -108,12 +108,6 @@ parameters:
 			count: 1
 			path: src/Store/StreamDoctrineDbalStoreStream.php
 
-		-
-			message: '#^Cannot use \+\+ on mixed\.$#'
-			identifier: preInc.type
-			count: 1
-			path: src/Store/TaggableDoctrineDbalStore.php
-
 		-
 			message: '#^Method Patchlevel\\EventSourcing\\Store\\TaggableDoctrineDbalStoreStream\:\:current\(\) never returns null so it can be removed from the return type\.$#'
 			identifier: return.unusedType

From e589cf208c23690554bd4a78bb262a689ac3d7a0 Mon Sep 17 00:00:00 2001
From: David Badura <david.badura@patchlevel.de>
Date: Thu, 4 Sep 2025 18:32:46 +0200
Subject: [PATCH 22/22] use identifier component

---
 src/DCB/AttributeEventTagExtractor.php        | 12 +--
 .../Normalizer/StringableNormalizer.php       | 85 -------------------
 src/Stringable.php                            | 16 ----
 .../SimpleSetupTaggableStoreBench.php         |  6 +-
 .../Course/CourseId.php                       |  6 +-
 .../Course/StudentId.php                      |  6 +-
 .../DCB/AttributeEventTagExtractorTest.php    |  2 +-
 7 files changed, 16 insertions(+), 117 deletions(-)
 delete mode 100644 src/Serializer/Normalizer/StringableNormalizer.php
 delete mode 100644 src/Stringable.php

diff --git a/src/DCB/AttributeEventTagExtractor.php b/src/DCB/AttributeEventTagExtractor.php
index 30e869e8..f9254902 100644
--- a/src/DCB/AttributeEventTagExtractor.php
+++ b/src/DCB/AttributeEventTagExtractor.php
@@ -5,9 +5,9 @@
 namespace Patchlevel\EventSourcing\DCB;
 
 use Patchlevel\EventSourcing\Attribute\EventTag;
-use Patchlevel\EventSourcing\Stringable;
+use Patchlevel\EventSourcing\Identifier\Identifier;
 use ReflectionClass;
-use Stringable as NativeStringable;
+use Stringable;
 
 use function array_keys;
 use function hash;
@@ -36,12 +36,12 @@ public function extract(object $event): array
 
             $value = $property->getValue($event);
 
-            if ($value instanceof Stringable) {
-                $value = $value->toString();
+            if ($value instanceof Stringable || is_int($value)) {
+                $value = (string)$value;
             }
 
-            if ($value instanceof NativeStringable || is_int($value)) {
-                $value = (string)$value;
+            if ($value instanceof Identifier) {
+                $value = $value->toString();
             }
 
             if (!is_string($value)) {
diff --git a/src/Serializer/Normalizer/StringableNormalizer.php b/src/Serializer/Normalizer/StringableNormalizer.php
deleted file mode 100644
index 537bdbaf..00000000
--- a/src/Serializer/Normalizer/StringableNormalizer.php
+++ /dev/null
@@ -1,85 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Patchlevel\EventSourcing\Serializer\Normalizer;
-
-use Attribute;
-use Patchlevel\EventSourcing\Stringable;
-use Patchlevel\Hydrator\Normalizer\InvalidArgument;
-use Patchlevel\Hydrator\Normalizer\InvalidType;
-use Patchlevel\Hydrator\Normalizer\Normalizer;
-use Patchlevel\Hydrator\Normalizer\TypeAwareNormalizer;
-use Symfony\Component\TypeInfo\Type;
-use Symfony\Component\TypeInfo\Type\ObjectType;
-
-use function is_a;
-use function is_string;
-
-/** @experimental */
-#[Attribute(Attribute::TARGET_PROPERTY | Attribute::TARGET_CLASS)]
-final class StringableNormalizer implements Normalizer, TypeAwareNormalizer
-{
-    public function __construct(
-        /** @var class-string<Stringable>|null */
-        private string|null $stringableClass = null,
-    ) {
-    }
-
-    public function normalize(mixed $value): string|null
-    {
-        if ($value === null) {
-            return null;
-        }
-
-        $class = $this->stringableClass();
-
-        if (!$value instanceof Stringable) {
-            throw InvalidArgument::withWrongType($class, $value);
-        }
-
-        return $value->toString();
-    }
-
-    public function denormalize(mixed $value): Stringable|null
-    {
-        if ($value === null) {
-            return null;
-        }
-
-        if (!is_string($value)) {
-            throw InvalidArgument::withWrongType('string', $value);
-        }
-
-        $class = $this->stringableClass();
-
-        return $class::fromString($value);
-    }
-
-    /** @return class-string<Stringable> */
-    public function stringableClass(): string
-    {
-        if ($this->stringableClass === null) {
-            throw InvalidType::missingType();
-        }
-
-        return $this->stringableClass;
-    }
-
-    public function handleType(Type|null $type): void
-    {
-        if ($type === null || $this->stringableClass !== null) {
-            return;
-        }
-
-        if (!$type instanceof ObjectType) {
-            return;
-        }
-
-        if (is_a($type->getClassName(), Stringable::class, true) === false) {
-            throw InvalidType::unsupportedType(Stringable::class, $type->getClassName());
-        }
-
-        $this->stringableClass = $type->getClassName();
-    }
-}
diff --git a/src/Stringable.php b/src/Stringable.php
deleted file mode 100644
index eeb96725..00000000
--- a/src/Stringable.php
+++ /dev/null
@@ -1,16 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Patchlevel\EventSourcing;
-
-use Patchlevel\EventSourcing\Serializer\Normalizer\StringableNormalizer;
-
-/** @experimental */
-#[StringableNormalizer]
-interface Stringable
-{
-    public function toString(): string;
-
-    public static function fromString(string $value): self;
-}
diff --git a/tests/Benchmark/SimpleSetupTaggableStoreBench.php b/tests/Benchmark/SimpleSetupTaggableStoreBench.php
index c70a889a..b0759142 100644
--- a/tests/Benchmark/SimpleSetupTaggableStoreBench.php
+++ b/tests/Benchmark/SimpleSetupTaggableStoreBench.php
@@ -4,7 +4,7 @@
 
 namespace Patchlevel\EventSourcing\Tests\Benchmark;
 
-use Patchlevel\EventSourcing\Aggregate\AggregateRootId;
+use Patchlevel\EventSourcing\Identifier\Identifier;
 use Patchlevel\EventSourcing\Message\Message;
 use Patchlevel\EventSourcing\Metadata\Event\AttributeEventRegistryFactory;
 use Patchlevel\EventSourcing\Repository\DefaultRepository;
@@ -24,8 +24,8 @@ final class SimpleSetupTaggableStoreBench
     private TaggableDoctrineDbalStore $store;
     private Repository $repository;
 
-    private AggregateRootId $singleEventId;
-    private AggregateRootId $multipleEventsId;
+    private Identifier $singleEventId;
+    private Identifier $multipleEventsId;
 
     public function setUp(): void
     {
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/CourseId.php b/tests/Integration/DynamicConsistencyBoundary/Course/CourseId.php
index 6a9fb704..80b7edc1 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/CourseId.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/CourseId.php
@@ -4,10 +4,10 @@
 
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course;
 
-use Patchlevel\EventSourcing\Aggregate\RamseyUuidV7Behaviour;
-use Patchlevel\EventSourcing\Stringable;
+use Patchlevel\EventSourcing\Identifier\Identifier;
+use Patchlevel\EventSourcing\Identifier\RamseyUuidV7Behaviour;
 
-final class CourseId implements Stringable
+final class CourseId implements Identifier
 {
     use RamseyUuidV7Behaviour;
 }
diff --git a/tests/Integration/DynamicConsistencyBoundary/Course/StudentId.php b/tests/Integration/DynamicConsistencyBoundary/Course/StudentId.php
index 49b5209e..6255a619 100644
--- a/tests/Integration/DynamicConsistencyBoundary/Course/StudentId.php
+++ b/tests/Integration/DynamicConsistencyBoundary/Course/StudentId.php
@@ -4,10 +4,10 @@
 
 namespace Patchlevel\EventSourcing\Tests\Integration\DynamicConsistencyBoundary\Course;
 
-use Patchlevel\EventSourcing\Aggregate\RamseyUuidV7Behaviour;
-use Patchlevel\EventSourcing\Stringable;
+use Patchlevel\EventSourcing\Identifier\Identifier;
+use Patchlevel\EventSourcing\Identifier\RamseyUuidV7Behaviour;
 
-final class StudentId implements Stringable
+final class StudentId implements Identifier
 {
     use RamseyUuidV7Behaviour;
 }
diff --git a/tests/Unit/DCB/AttributeEventTagExtractorTest.php b/tests/Unit/DCB/AttributeEventTagExtractorTest.php
index 84afd8c6..eb45e28c 100644
--- a/tests/Unit/DCB/AttributeEventTagExtractorTest.php
+++ b/tests/Unit/DCB/AttributeEventTagExtractorTest.php
@@ -4,9 +4,9 @@
 
 namespace Patchlevel\EventSourcing\Tests\Unit\DCB;
 
-use Patchlevel\EventSourcing\Aggregate\CustomId;
 use Patchlevel\EventSourcing\Attribute\EventTag;
 use Patchlevel\EventSourcing\DCB\AttributeEventTagExtractor;
+use Patchlevel\EventSourcing\Identifier\CustomId;
 use PHPUnit\Framework\TestCase;
 
 final class AttributeEventTagExtractorTest extends TestCase