OAuth 2.0 Concepts

Authorization Code Flow (Most Common)

1. Client redirects user to Auth Server
2. User logs in, grants consent
3. Auth Server returns authorization code
4. Client exchanges code for tokens
5. Client uses access token for API

Grant Types

Grant Type	Use Case
Authorization Code	Web apps (most secure)
PKCE	Mobile/SPA (no client secret)
Client Credentials	Service-to-service
Password	Legacy (deprecated)

Key Points

• Understanding OAuth 2.0 is essential for production systems
• Always consider scalability and maintainability
• Test thoroughly before deploying to production
• Monitor performance and set up alerting

Common Patterns

1. Validation: Always validate input at the boundary
2. Error Handling: Use structured error responses
3. Logging: Log key events for debugging
4. Testing: Unit, integration, and load tests
5. Documentation: Keep docs updated with code changes

Security Best Practices

1. Password Storage: Use bcrypt/scrypt with salt
2. Token Management: Short-lived access tokens (15-30 min)
3. HTTPS: Enforce TLS everywhere
4. Rate Limiting: Prevent brute force attacks
5. Input Validation: Never trust user input

Implementation Checklist

• Hash passwords with bcrypt (cost factor 12+)
• Implement token refresh flow
• Add CSRF protection
• Log authentication events
• Use secure session management

Key Points

• Understanding OAuth 2.0 is essential for production systems
• Always consider scalability and maintainability
• Test thoroughly before deploying to production
• Monitor performance and set up alerting

Common Patterns

1. Validation: Always validate input at the boundary
2. Error Handling: Use structured error responses
3. Logging: Log key events for debugging
4. Testing: Unit, integration, and load tests
5. Documentation: Keep docs updated with code changes