Why microservices have their own database?

Should microservices have their own DB?

As you described it very well above, each microservice needs to own it's DATA, which could be held within a dedicated database, within a dedicated schema (within a database), or even a set of dedicated tables (within a schema within a database).

Why do microservices need to separate databases?

Creating a separate database for each service helps to enforce domain boundaries, but it's only one approach. There's nothing stopping you from having all your services share the same database. As long as your services behave and don't do unexpected things to data owned by other services, you'll be fine.

Does microservices have same database?

In the shared-database-per-service pattern, the same database is shared by several microservices. You need to carefully assess the application architecture before adopting this pattern, and make sure that you avoid hot tables (single tables that are shared among multiple microservices).

Is it a good idea for microservices to share a common database?

I've seen folks refer to this idea in part, trivially, as “each microservice should own and control its own database and no two services should share a database.” The idea is sound: don't share a single database across services because then you run into conflicts like competing read/write patterns, data-model conflicts ...