Different credentials for PostgreSQL Read Replicas
Right now replicas have the same credentials as the primary database.
This limits its usefulness as a way to provide certain people or applications with read-only access.
In addition to that, it means the Replica database is incompatible with Ruby on Rails's native "multiple database" functionality as it requires having a distinct user for each database:
>> Second, the username for the writers and replicas should be different, and the replica user's database permissions should be set to only read and not write.
I expect few customers needing to specify their own credentials. Anything that is different from the primary database should suffice both use cases.