[jkarneges]

I'd agree there is an arguable difference between sharing a server vs sharing data within the server.

Bottleneck issues aside, letting two microservices connect to the same Postgres cluster but access different "databases" (collection of tables) within that cluster could be considered an acceptable data separation. Certainly with multi-tenant DBaaS systems there may be some server sharing by unrelated microservices/customers. Whereas letting two microservices access the same database tables would probably be frowned upon.

Nevertheless, sharing the same Kafka topics between microservices seems to be a common thing to do.

[ivalm]

> Whereas letting two microservices access the same database tables would probably be frowned upon.

> Nevertheless, sharing the same Kafka topics between microservices seems to be a common thing to do.

I think if it is part of one whole isn’t this fine? You have one service that generates customer facing output, you may have another service that powers analytics/dashboards you may have yet another service that ETLs data into some data mart. Why wouldn’t they touch the same table/subscribe to the same topic (since they just need read-only access to the data)? Genuinely curious what the problem is except for bottleneck/performance; and if it just bottleneck then wouldn’t scaling horizontally solve it?

[jkarneges]

Sure. I believe microservice boundaries are more about development agility rather than scalability. By limiting each microservice to a minimal API surface and a "2 pizza" team, everyone can iterate faster. And if a particular microservice is implemented as multiple sub-services sharing database tables only known by the team in charge, that seems fine.