Synchronous messaging

When a timely response is expected from a service by a system and the system waits on it till a response is received from the service, it is synchronous messaging. What's left is the most sought-after choice in the case of microservices. It is simple and supports HTTP request-response, thereby leaving little room to look for an alternative. This is also one of the reasons that most implementations of microservices use HTTP (API-based styles).