An API is a contract.If you break it, you break trust. Designing a good API requires foresight, consistency, and a deep understanding of how other developers will consume your work.
1. Versioning is Mandatory
Never release an API without a version number in the URL(e.g., /api/v1/users). Two years from now, you will need to change the data structure. Without versioning, you break every mobile app currently installed on users' phones. With versioning, you release v2 while v1 keeps running for legacy clients.
2. Use Standard HTTP Status Codes
Don't send a 200 OK response that contains "error": "User not found" in the JSON body. That's lying.
- 200: Success
- 201: Created (for POST requests)
- 400: Bad Request (Client sent garbage)
- 401: Unauthorized (Who are you?)
- 403: Forbidden (I know who you are, but you can't touch this)
- 404: Not Found
- 500: Server Error (Our fault)
3. Pagination from Day One
You might only have 10 users today, but you'll have 10,000 next year. An endpoint returning GET /users attempting to return 10k rows will crash your database and timeout the client. Always implement limit/offset or cursor-based pagination defaults.
4. Rate Limiting
Protect your resources. A single buggy loop in a client script can inadvertently DDoS your API. Implement token bucket rate limiting (e.g., 100 requests per minute per IP) to ensure stability for everyone.