If you need microservice architecture, it's likely because either the size or the rate of change of your data prevent you from using a single RDBMS with synchronous transactions. So your microservices talk to something like Cassandra.
You might want some of the advantages of microservices without yet reaching this scale. Then you likely have most microservices stateless, and can admit you have a single database where you can do joins (but not updates) across microservice borders.
You might want some of the advantages of microservices without yet reaching this scale. Then you likely have most microservices stateless, and can admit you have a single database where you can do joins (but not updates) across microservice borders.