When it comes to the communication layer between microservices, synchronous is certainly the most widely used approach. Within this topic, some protocols are well known and others less so. The range of direct protocols is as follows:

HTTP

TCP

WebSockets

Sockets

RPC

SOAP

Arguably, the most commonly implemented is HTTP. Many microservices use HTTP to communicate with each other, where as the HTTP is typically used with JSON.

The problem with this approach is that, with HTTP, JSON can generate an unwanted processing time to send and translate the information. Some teams that use JSON with HTTP only adopt the keep alive strategy for app-to-app communication and conventional connections to APIs.

When it comes to HTTP, API with JSON is practically normative. However, for internal communication between microservices, this is quite questionable. A good approach, in this case, considering problems of latency and data translation, is the use of binary traffic for communication between microservices.

There are some very interesting options for this approach: Avro, Protocol Buffer with CPRM, and Thrift are some examples. Another important point is that with binary we are not tied to any specific technology, and changing the communication interface with this technology is extremely simpl