There are 2 type APIs sync communication in microservices:

▪ Public APIs: API calls from the client apps.

▪ Backend APIs: inter-service communication between backend

services.

▪ Public APIs

Use RESTful APIs over HTTP protocol. RESTful APIs use

JSON payloads for request-response, that easy to check

payloads and easy agreement with clients.

▪ Backend APIs

Inter-service communication can result in a lot of network

traffic. serialization speed and payload size become more

important. Using gRPC is mandatory for increase network

performance.

https://medium.com/design-microservices-architecture-with-patterns/microservices-communications-f319f8d76b71