Microservices Development Cookbook

Identifying bounded contexts

When designing microservices, a common point of confusion is how big or small a service should be. This confusion can lead engineers to focus on things such as the number of lines of code in a particular service. Lines of code are an awful metric for measuring software; it's much more useful to focus on the role that a service plays, both in terms of the business capability it provides and the domain objects it helps manage. We want to design services that have low coupling with other services, because this limits what we have to change when introducing a new feature in our product or making changes to an existing one. We also want to give services a single responsibility. 

When decomposing a monolith, it's often ...