API Design Principles

Introduction

Good API design is crucial for developer experience. This document outlines the core principles we follow when designing REST APIs.

Principle 1: Use Nouns, Not Verbs

URLs should represent resources, not actions. Use HTTP methods to indicate the action.

Good:

• GET /users/123
• POST /orders
• DELETE /products/456

Bad:

• GET /getUser?id=123
• POST /createOrder
• GET /deleteProduct/456

Principle 2: Use Plural Nouns

Always use plural nouns for consistency.

• /users (not /user)
• /orders (not /order)
• /products (not /product)

Principle 3: Hierarchical Relationships

Express relationships through URL hierarchy.

• GET /users/123/orders - Get all orders for user 123
• GET /users/123/orders/456 - Get specific order 456 for user 123

Principle 4: Filtering and Pagination

Use query parameters for filtering, sorting, and pagination.

• GET /products?category=electronics&sort=price&page=2&limit=20

Principle 5: Versioning

Always version your APIs. We prefer URL versioning.

• /v1/users
• /v2/users

Principle 6: Error Handling

Return consistent error responses with appropriate HTTP status codes.

{
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Email format is invalid",
    "field": "email"
  }
}

Principle 7: Rate Limiting

Implement rate limiting and communicate limits via headers:

• X-RateLimit-Limit: 1000
• X-RateLimit-Remaining: 999
• X-RateLimit-Reset: 1640000000

Conclusion

Following these principles leads to APIs that are intuitive, consistent, and easy to maintain. Remember: the best API is one that developers can use without reading documentation.