While REST (HTTP-based) is common for public APIs, internal communication between microservices often uses RPC (Remote Procedure Call) for better performance and type safety.

1. What is RPC?

RPC is a protocol that allows a program to execute a procedure (function) in another address space (commonly on another machine) as if it were a local function call.

• Abstraction: The developer doesn't need to worry about the details of network communication.
• Efficiency: Often uses binary serialization instead of text (JSON/XML), making it faster and smaller.

2. gRPC (Google RPC)

gRPC is a modern high-performance RPC framework developed by Google. It is the de-facto standard for microservices communication.

• Protocol Buffers (Protobuf): Uses Protobuf as the Interface Definition Language (IDL) and message serialization format.
• HTTP/2: Built on top of HTTP/2, allowing features like bidirectional streaming and multiplexing.
• Language Agnostic: You can have a server in Go and a client in Python, and they can communicate seamlessly using generated code.

3. Protobuf Example

Protobuf is a binary format, so it's much smaller than JSON. You define your data structure in a .proto file:

1syntax = "proto3";
2
3message UserRequest {
4  string user_id = 1;
5  uint32 version = 2;
6}
7
8message UserResponse {
9  string name = 1;
10  string email = 2;
11}
12
13service UserService {
14  rpc GetUser (UserRequest) returns (UserResponse);
15}

RPC vs REST