What Is gRPC?

Explains the concepts behind gRPC.
Tags:

What Is gRPC?

gRPC is a high-performance, general-purpose open source RPC (Remote Procedure Call) framework developed by Google for fast and efficient communication between services.

It lets you call a function across a network as though it were a function in your own code. It standardizes remote function calls and enables fast, type-safe communication.

Unlike traditional REST communication, which commonly uses HTTP/1.1 and JSON, gRPC uses HTTP/2 and the binary Protocol Buffers (ProtoBuf) serialization format. This provides low latency, high throughput, and compact messages.

Service APIs are specified in .proto files. Servers and clients share the same interface definitions, and Stub code can be generated automatically for multiple programming languages. This improves development in polyglot environments and makes service boundaries easier to maintain.

gRPC Flow Source: https://appmaster.io/ko/blog/grpcneun-mueosibnigga

Core gRPC Elements

1. Based on Protocol Buffers

gRPC uses the binary Protocol Buffers format instead of JSON.

  • Smaller and faster than JSON
  • Based on an explicit schema in a protobuf file
  • Automatically generates Stub code for clients and servers in each language

Example: hello.proto

service HelloService {
  rpc SayHello (HelloRequest) returns (HelloResponse);
}

message HelloRequest {
  string name = 1;
}

message HelloResponse {
  string message = 1;
}

2. HTTP/2 Communication

gRPC uses HTTP/2 internally, enabling:

  • Multiplexing: multiple requests over one connection
  • Server Push
  • Header compression
  • Streaming, including bidirectional streaming

This makes it faster and more efficient than REST for suitable workloads.

Four gRPC Communication Types

Type Description
Unary One request and one response
Server Streaming The server delivers multiple messages as a stream
Client Streaming The client sends multiple messages and the server responds once
Bidirectional Streaming The client and server exchange multiple messages concurrently

Suitable for chat, real-time log processing, and streaming data processing.

Advantages and Disadvantages

Advantages

  • Fast, lightweight communication through Protocol Buffers and HTTP/2
  • Strong type safety with compile-time validation based on proto schemas
  • Support for languages including Go, Java, Kotlin, Python, Rust, C#, Node, and Ruby
  • Built-in bidirectional streaming
  • Well suited to internal microservice communication

Disadvantages

  • Difficult to call directly from browsers without gRPC-Web or WebAssembly
  • Developers must understand proto authoring and compilation
  • More difficult to debug than REST

When Should You Use gRPC?

Suitable Cases

  • Internal microservice communication
  • High-performance traffic
  • Real-time streaming services
  • Polyglot services, such as a Java server and Go client
  • IoT, game servers, and real-time event processing

When REST Is Better

  • APIs called directly by browsers
  • Simple public APIs
  • Cases that require human-readable formats such as JSON

gRPC vs REST

Category gRPC REST
Communication protocol HTTP/2 Usually HTTP/1.1, although HTTP/2 is possible
Data format Binary Protocol Buffers Text formats such as JSON and XML
Speed Very fast, compact, and efficient to parse Relatively slower
Streaming Full support, including bidirectional streaming Limited; requires SSE or WebSocket separately
Interface definition Types and schemas defined in .proto files No required schema; OpenAPI is recommended
Type safety Compile-time validation Often validated at runtime
Code generation Automatic client and server Stub generation Documentation through Swagger/OpenAPI; Stubs are optional
Ease of use Browser calls require gRPC-Web Directly usable from browsers and JavaScript
Human readability Low due to binary format High with readable JSON
Debugging More difficult Easier with curl and Postman
Security Strong TLS and HTTP/2 combination Standard TLS security
Best suited for Internal microservices, high performance, real-time streaming Public APIs, external integrations, browser-centric services
Language support Official support for nearly every major language Language-neutral when HTTP is supported
Summary of advantages Fast, efficient, type-safe, strong streaming Simple, easy to debug, highly compatible
Summary of disadvantages Complex, limited browser accessibility Lower performance, weaker type safety

Conclusion

  • gRPC: Best for internal communication, high performance, and streaming.
  • REST: Best for browsers, public APIs, and convenient debugging.