API Design

TL;DR

REST: HTTP methods on resources. GraphQL: Client specifies data. gRPC: Binary protocol. Rate limiting: Prevent abuse. Versioning: Support old clients.

REST (Representational State Transfer)

GET    /api/v1/users           → List
GET    /api/v1/users/123       → Get one
POST   /api/v1/users           → Create
PUT    /api/v1/users/123       → Update (full)
PATCH  /api/v1/users/123       → Update (partial)
DELETE /api/v1/users/123       → Delete

Best practices: Use nouns not verbs, plural resources, query params for filtering.

GraphQL

query {
  user(id: "123") {
    name
    email
    posts(limit: 5) { title }
  }
}

Benefits: No over-fetching, single request for nested data.

gRPC

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

Benefits: Binary (7x smaller), type-safe, bi-directional streaming.

Comparison

Aspect	REST	GraphQL	gRPC
Simplicity	✅ Simple	❌ Complex	❌ Complex
Performance	🟡 OK	🟡 OK	✅ Fast
Caching	✅ HTTP	❌ Custom	❌ None
Browser	✅ Native	✅ Native	❌ Proxy

Rate Limiting

def rate_limit(user_id, limit=100, window=60):
    key = f"rate_limit:{user_id}"
    current = redis.incr(key)
    if current == 1:
        redis.expire(key, window)
    if current > limit:
        raise RateLimitExceeded()

Response: 429 Too Many Requests with Retry-After header.

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