Amazon RDS for PostgreSQL has support for storage autoscaling which allows us to define an upper bound for storage, and then RDS automatically scales up capacity as storage utilization increases.

See:

• https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_PIOPS.StorageTypes.html#USER_PIOPS.Autoscaling
• https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/db_instance#storage-autoscaling