[dalberto]

I generally agree that one database instance is ideal, but there are other reasons why Postgres everywhere is advantageous, even across multiple instances:

- Expertise: it's just SQL for the most part - Ecosystem: same ORM, same connection pooler - Portability: all major clouds have managed Postgres

I'd gladly take multiple Postgres instances even if I lose cross-database joins.

[throwaway7783]

Yep. If performance becomes a concern, but we still want to exploit joins etc, it's easy to set up replicas and "shard" read only use cases across replicas.

[nicholasjarnold]

Postgres supports the Foreign Data Wrapper concept from SQL/MED. If you configure this you can do joins across instances, even!

https://www.postgresql.org/docs/current/postgres-fdw.html