Comment by doctor_eval

I agree that 1BDB is a good idea, but having one ginormous schema has its own costs. So I still think data should be logically partitioned between applications/microservices - in PG terms, one “cluster” but multiple “databases”.

We solved the problem of collecting data from the various databases for end users by having a GraphQL layer which could integrate all the data sources. This turned out to be absolutely awesome. You could also do something similar using FDW. The effort was not significant relative to the size of the application.

The benefits of this architecture were manifold but one of the main ones is that it reduces the complexity of each individual database, which dramatically improved performance, and we knew that if we needed more performance we could pull those individual databases out into their own machine.