APIs power every modern application — mobile apps, microservices, dashboards, IoT devices, and more. And today, developers have three major API technologies to choose from:

  • REST (HTTP/JSON)
  • gRPC (HTTP/2 + Protocol Buffers)
  • GraphQL (single endpoint + flexible queries)

Each has its strengths, weaknesses, and ideal use cases.

🌐 1. REST — The Traditional Standard

REST is the most widely used API style, built around:

  • Resources (/users, /orders)
  • HTTP verbs (GET, POST, PUT, DELETE)
  • JSON as the default format

✔ Strengths

  • Easy to understand
  • Browser-friendly
  • Great tooling
  • Good for public APIs

❌ Weaknesses

  • Over-fetching
  • Under-fetching
  • JSON overhead
  • HTTP/1.1 latency

Java Example

@RestController
@RequestMapping("/users")
public class UserController {

    @GetMapping("/{id}")
    public User getUser(@PathVariable int id) {
        return new User(id, "John Doe");
    }
}

⚡ 2. gRPC — High-Performance, Low-Latency APIs

gRPC uses:

  • HTTP/2
  • Protocol Buffers
  • Generated client/server code
  • Streaming

✔ Strengths

  • Extremely fast
  • Small binary payloads
  • Streaming support
  • Strong typing

❌ Weaknesses

  • Not browser-native
  • Harder to debug binary payloads

gRPC Java Example

user.proto:

syntax = "proto3";

service UserService {
  rpc GetUser(GetUserRequest) returns (GetUserResponse);
}

message GetUserRequest {
  int32 id = 1;
}

message GetUserResponse {
  int32 id = 1;
  string name = 2;
}

Server:

public class UserServiceImpl extends UserServiceGrpc.UserServiceImplBase {

    @Override
    public void getUser(GetUserRequest request, StreamObserver<GetUserResponse> responseObserver) {

        GetUserResponse response = GetUserResponse.newBuilder()
                .setId(request.getId())
                .setName("John Doe")
                .build();

        responseObserver.onNext(response);
        responseObserver.onCompleted();
    }
}

🔍 3. GraphQL — Flexible Queries for Frontend Apps

GraphQL allows clients to request exactly the data they need.

✔ Strengths

  • Avoids over-fetching
  • Strong schema
  • Great for mobile & dashboards

❌ Weaknesses

  • Harder caching
  • Over-fetching risks in resolvers
  • Performance overhead in large graphs

Java Example (Spring GraphQL)

Schema:

type User {
  id: Int
  name: String
}

type Query {
  user(id: Int!): User
}

Resolver:

@Component
public class UserQueryResolver implements GraphQLQueryResolver {
    public User user(int id) {
        return new User(id, "John Doe");
    }
}

🏎 Performance Comparison

Feature REST gRPC GraphQL
Transport HTTP/1.1 HTTP/2 HTTP/1.1
Format JSON ProtoBuf (binary) JSON
Speed Medium Fastest Medium
Streaming ❌ No ✔ Yes ⚠ Partial
Browser support ✔ Excellent ⚠ Needs gRPC-Web ✔ Excellent
Typing Weak Strong Strong
Ideal for Public APIs Microservices Frontend apps

🎯 When to Choose What?

✔ Use REST when:

  • Building public APIs
  • Browser-based clients
  • Simplicity matters

✔ Use gRPC when:

  • You need performance
  • Microservices communicate internally
  • You need streaming

✔ Use GraphQL when:

  • Frontend needs flexible queries
  • You want to avoid over-fetching
  • Mobile apps require optimized data loads

🧠 Final Summary

  • REST → Simple, universal
  • gRPC → Fast, efficient, best for microservices
  • GraphQL → Flexible, client-driven

Each excels in different scenarios.