What design aspect is recommended when refactoring a monolithic application into microservices?

Creating an API contract agreement between the microservice implementation and its caller is essential in a microservices architecture. This contract serves as a clear, defined communication protocol that outlines how the services will interact with each other. By establishing a contract, developers can ensure that any changes made to one microservice won’t inadvertently break functionality in another service that relies on it. This is crucial in maintaining the independence of microservices, as each service can evolve at its own pace without tightly coupling changes to others.

Furthermore, an API contract helps to standardize interactions and provides a framework for testing, documentation, and maintaining service boundaries, which are crucial elements in a microservices design. In addition, it allows for the implementation of strategies for versioning and backward compatibility, facilitating smoother integration and deployment processes across the entire system.

The other options, while they may seem relevant, do not align as closely with the key principles of microservice design. For instance, developing microservice code in the same programming language can limit flexibility and the advantages of polyglot programming, while requiring synchronous communication can lead to tighter coupling and potential performance bottlenecks. Lastly, while implementing a versioning scheme is important, it often stems from the agreement established in the API contract rather than being a