Building Secure APIs: OAuth2, JWT, and Best Practices
Ryan Schaller
Principal, Coolradish
Your API is your product's foundation. Whether you're building a mobile app, a web application, or a platform for third-party developers, your API security determines whether you have a business or a liability. Let's build it right from the start.
OAuth2: The Industry Standard
OAuth2 isn't just for 'Login with Google' buttons—it's a comprehensive framework for secure API authorization. Understand the different flows: authorization code for web apps, PKCE for mobile apps, client credentials for service-to-service communication. Don't use the implicit flow—it's deprecated for good security reasons.
JWT Tokens: Power and Pitfalls
JSON Web Tokens are powerful but dangerous when misused. Always verify signatures. Never put sensitive data in the payload—it's base64 encoded, not encrypted. Use short expiration times and implement refresh token rotation. Store them securely—local storage is convenient but vulnerable to XSS attacks.
Rate Limiting and Throttling
Implement rate limiting from day one. Not just to prevent abuse—to ensure fair resource allocation and protect your infrastructure from unexpected spikes. Use different limits for different endpoints based on computational cost. Provide clear feedback when users hit limits.
API Key Management
If you're offering API access to developers, treat API keys like passwords. Support key rotation. Implement scoped permissions. Log all API key usage. Detect and alert on unusual patterns. Make it easy for users to revoke and regenerate keys.
Monitoring and Audit Logs
Log everything related to authentication and authorization. Who accessed what, when, and from where. Failed authentication attempts. Permission changes. Not just for security—these logs are invaluable for debugging and understanding user behavior. But ensure you're compliant with data privacy regulations.
Key Takeaway
API security isn't a one-time implementation—it's an ongoing practice. Start with solid fundamentals: OAuth2 for authorization, JWT for tokens, comprehensive logging, and rate limiting. Then iterate based on your specific threat model and compliance requirements. Your future enterprise customers will thank you.
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