What is gRPC?

gRPC is a high-performance RPC (Remote Procedure Call) framework developed by Google. It uses Protocol Buffers for serialization and HTTP/2 for transport.

gRPC vs REST

Aspect	gRPC	REST
Protocol	HTTP/2	HTTP/1.1 or HTTP/2
Serialization	Protocol Buffers (binary)	JSON (text)
Contract	Strict (.proto files)	Loose (OpenAPI optional)
Streaming	Built-in	Requires WebSocket/SSE
Browser support	Limited	Native
Performance	Faster	Slower

Protocol Buffers

Define your service and messages in .proto files:

syntax = "proto3";

service UserService {
  rpc GetUser (GetUserRequest) returns (User);
  rpc ListUsers (ListUsersRequest) returns (stream User);
}

message GetUserRequest {
  int32 id = 1;
}

message User {
  int32 id = 1;
  string name = 2;
  string email = 3;
}

Communication Patterns

Unary RPC

Client ─── Request ───► Server
Client ◄── Response ─── Server

Server Streaming

Client ─── Request ───────► Server
Client ◄── Response 1 ───── Server
Client ◄── Response 2 ───── Server
Client ◄── Response N ───── Server

Client Streaming

Client ─── Request 1 ────► Server
Client ─── Request 2 ────► Server
Client ─── Request N ────► Server
Client ◄── Response ────── Server

Bidirectional Streaming

Client ◄──► Server (both send streams)

Benefits

Benefit	Description
Performance	Binary format, HTTP/2 multiplexing
Type safety	Generated code from proto files
Streaming	Native support for all patterns
Code generation	Auto-generate client/server code
Language agnostic	Support for many languages

When to Use gRPC

Good for:

Microservices communication
Low-latency, high-throughput systems
Streaming data
Polyglot environments

Not ideal for:

Browser clients (limited support)
Simple CRUD APIs
When human-readable format needed

Interview Tips

Explain Protocol Buffers and binary serialization
Know the four communication patterns
Compare performance with REST
Discuss when to choose gRPC vs REST
Mention HTTP/2 benefits (multiplexing)

gRPC

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