API Design Best Practices: Building Developer-Friendly APIs

API Design Best Practices: Building Developer-Friendly APIs | DevPrep

Good API design is invisible. Bad API design causes endless support tickets. Here's what I've learned designing APIs at Google.

URL Structure

Response Format

Pagination Strategies

Strategy	Pros	Cons
Offset/Limit	Simple, random access	Inconsistent with inserts/deletes
Cursor-based	Consistent, performant	No random page access
Keyset	Very fast, consistent	Requires sortable unique column

Versioning

Rate Limiting Headers

Golden Rules

Be consistent (naming, casing, error format)
Use HTTP status codes correctly (don't return 200 for errors)
Include request IDs for debugging
Document everything (OpenAPI/Swagger)
Version from day one

// Good: nouns, not verbs
GET    /api/v1/users          // List users
GET    /api/v1/users/123      // Get user
POST   /api/v1/users          // Create user
PUT    /api/v1/users/123      // Replace user
PATCH  /api/v1/users/123      // Partial update
DELETE /api/v1/users/123      // Delete user

// Bad
GET    /api/getUsers
POST   /api/createUser
POST   /api/deleteUser/123

// Success
{
  "data": { "id": "123", "name": "Rahul" },
  "meta": { "requestId": "abc-123" }
}

// Error
{
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Email is required",
    "details": [
      { "field": "email", "message": "Must be a valid email address" }
    ]
  },
  "meta": { "requestId": "abc-124" }
}

// List with pagination
{
  "data": [...],
  "pagination": {
    "page": 1,
    "pageSize": 20,
    "totalCount": 150,
    "totalPages": 8
  }
}

API Design Best Practices: Building Developer-Friendly APIs

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URL Structure

Response Format

Versioning

Rate Limiting Headers

Golden Rules