When developing reactive microservices, it is not always obvious when to use non-blocking synchronous APIs and when to use event-driven asynchronous services. In general, to make a microservice robust and scalable, it is important to make it as autonomous as possible, for example, minimizing its runtime dependencies. This is also known as loose coupling. Therefore, asynchronous message passing of events, is preferable over synchronous APIs. This is because the microservice will only depend on access to the messaging system at runtime instead of being dependent on synchronous access to a number of other microservices.
There are, however, a number of cases where non-blocking synchronous APIs could be favorable to use, for example:
- For read operations where an end user is waiting...
