REST vs gRPC vs GraphQL: API Communication Protocols Compared

There's more than one way to exchange data between backend services or between client and backend. The three most popular: REST, gRPC, and GraphQL. Which is best? Answer: "It depends."

REST (Representational State Transfer)

Resource-based communication over HTTP. The standard API approach since the 2000s.

GET    /api/users          → List all users
GET    /api/users/42       → Get user by ID
POST   /api/users          → Create user
PUT    /api/users/42       → Update user
DELETE /api/users/42       → Delete user

Pros: Simple, ubiquitous, built-in caching, universal support Cons: Over-fetching, under-fetching, versioning complexity

gRPC (Google Remote Procedure Call)

High-performance RPC framework using Protocol Buffers (binary serialization).

service UserService {
  rpc GetUser (UserRequest) returns (UserResponse);
  rpc ListUsers (Empty) returns (stream UserResponse);
}

Pros: Extreme performance, HTTP/2 multiplexing, type safety, streaming, code generation Cons: Limited browser support, binary debugging is hard, steeper learning curve

GraphQL

Query language developed by Facebook where clients request exactly the data they need:

query {
  user(id: 42) {
    name
    email
    posts(limit: 5) {
      title
      createdAt
    }
  }
}

Pros: No over/under-fetching, single endpoint, strong type system, great for relational data Cons: Complex caching, N+1 query problem, overkill for simple CRUD

Comparison Table

| Feature | REST | gRPC | GraphQL | |---------|------|------|---------| | Protocol | HTTP/1.1 | HTTP/2 | HTTP/1.1 | | Data format | JSON | Protobuf (binary) | JSON | | Performance | Medium | Very high | Medium | | Learning curve | Low | High | Medium | | Browser support | ✅ Full | ⚠️ Limited | ✅ Full | | Streaming | ❌ | ✅ | ⚠️ Subscriptions | | Caching | ✅ Easy | ❌ Hard | ⚠️ Complex | | Type safety | ❌ | ✅ | ✅ |

When to Use Each

REST — Public APIs, simple CRUD, caching matters

gRPC — Inter-service communication, high performance, streaming

GraphQL — Complex relational data, mobile apps (bandwidth savings)

Hybrid Approach

In practice, most systems use multiple protocols together:

Client (Web/Mobile) ←→ GraphQL/REST ←→ API Gateway
                                            ↓
Service A ←→ gRPC ←→ Service B

Conclusion

There's no single "best" protocol. REST for simplicity, gRPC for performance-critical inter-service communication, and GraphQL for complex frontend needs.

Learn API design and microservice communication patterns in the Software Architecture 3.0 book.