Defining a microservice

A microservice architecture is about splitting up monolithic applications into smaller components, which achieves two major goals:

• Faster development, enabling continuous deployments
• Easier to scale, manually or automatically

A microservice is essentially an autonomous software component that is independently upgradeable, replaceable, and scalable. To be able to act as an autonomous component, it must fulfill certain criteria, as follows:

• It must conform to a shared-nothing architecture; that is, microservices don’t share data in databases with each other!
• It must only communicate through well-defined interfaces, either using APIs and synchronous services or preferably by sending messages asynchronously. The APIs and message formats used must be stable, well documented, and evolve by following a defined versioning strategy.
• It must be deployed as separate runtime processes. Each instance of a microservice...