The first step is to understand the functioning of the microservice to know what kind of communication best applies. Take, for example, the microservice recommendations. It is a microservice that has no direct communication with the customer, but traces a user's profile. No other application point expects an immediate response arising from this microservice. Thus, the communication model for this microservice is asynchronous.

Very well! We saw that RecommendationService is not a synchronous case; then what is?

The answer is UserService. When a user enters a given API that communicates with UserService, this user sees the change immediately. When a microservice requests some information on the requested UserService, we want the most current information possible and immediately. Yes, UserService is a service where synchronous communication can be applied.

But how can we create a good layer of synchronous communication between microservices? The answer is right in the next section.