I don't think it's a hard prerequisite (as there really aren't... too many of those, microservices can be built how you want them to be), but I think it's a goo

I don't think it's a hard prerequisite (as there really aren't... too many of those, microservices can be built how you want them to be), but I think it's a good rule to follow. If consistency is a necessary concern, and you have tightly coupled data, it's not a terrible idea to make the services a little bigger. But also, if you have a service that depends on multiple other services to do work, I don't think it's so bad to get used to using the API for the other services (rather than trying to access their databases directly) -- despite the introduced latency overhead