Introduction
After building APIs for organizations of all sizes, certain patterns emerge repeatedly. Here are the lessons we've learned.
Versioning Done Right
API versioning is inevitable. Plan for it:
- Use URL versioning (`/v1/`, `/v2/`) for simplicity
- Maintain backwards compatibility within major versions
- Document deprecation timelines clearly
Error Handling
Consistent error responses save debugging time:
Standard Format
```json
{
"error": {
"code": "VALIDATION_ERROR",
"message": "Invalid request parameters",
"details": [
{ "field": "email", "message": "Invalid format" }
]
}
}
```
HTTP Status Codes
Use them correctly:
- 400 for client errors
- 401 for authentication issues
- 403 for authorization issues
- 404 for not found
- 500 for server errors
Rate Limiting
Protect your API from abuse:
- Implement per-client limits
- Return `429 Too Many Requests` with `Retry-After` header
- Consider tiered limits for different client types
Documentation
Good documentation is a competitive advantage:
- Use OpenAPI/Swagger specifications
- Provide working examples
- Include authentication details
- Document rate limits and quotas
Security Considerations
Authentication
- Use OAuth 2.0 / OpenID Connect
- Implement proper token validation
- Support refresh tokens for long sessions
Authorization
- Implement scope-based access control
- Validate permissions on every request
- Log access attempts for audit
Conclusion
Well-designed APIs are the foundation of modern software. Invest in getting the fundamentals right, and your integrations will be smoother for years to come.