Philosophically, is it really a "microservice" if it doesn't have its own database? In my opinion, if multiple services are ultimately all connecting to and storing their data in the same database, then you haven't really gained very much, since one misbehaving client can still take down everyone else's service. The point of microservices was always sold to me as "every team owns their own stack", and specifically if one team's stack goes down, everyone else can cheerfully continue. (Or less cheerfully, if the team whose stack went down was identity or user service.)