Part of the expense of microservices is that they be individually replaceable. Every microservice has dependencies to the interface of other services, and only

Part of the expense of microservices is that they be individually replaceable. Every microservice has dependencies to the interface of other services, and only the interface, which is typically RESTful. Refactoring in one code-base (read: one microservice), would never effect another code-base. The unit of reuse in this architecture tends to be the entire API, or libraries published as open source. If there is generic code that is suitable for a library, it is also suitable for contribution. If there is a core business function that should be reused, it is a microservice with an API and gets shared and consumed that way. Our hard rule for refactoring or enhancing services is if it is a breaking change: use another name (Rich Hickey's recommendation). If you provide more or accept less, fine. If you provide less, or require more, use a new route (like a /v2...). Therefore, refactoring in your code base, which makes your life easier, is transparent to everyone else who depends on your code. We have many small teams, so each team is providing 5 to 10 microservices, and refactoring within each independent repo is simple and low impact. There's no magic here, we simply paid the upfront cost of adopting an architecture that can be fielded by a very large dev organization, with a concerted effort in high quality DevOps practices. This move was also a means to scale the organization without dragging our efforts to a screeching halt with maintenance burden.