Single code base

The code base principle advices that each application should have a single code base. There can be multiple instances of deployment of the same code base, such as development, testing, or production. The code is typically managed in a source-control system such as Git, Subversion, and so on:

Extending the same philosophy for microservices, each microservice should have its own code base, and this code base is not shared with any other microservice. It also means that one microservice will have exactly one code base.