Authentication

Patterns for implementing authentication correctly: password hashing strategy, token design, session management, OAuth flows, and security hardening. Language-agnostic principles; JWT/OAuth examples use Node.js.

When to Use

• Implementing login, registration, or logout
• Designing JWT or session-based auth
• Integrating OAuth / OIDC providers (Google, GitHub, etc.)
• Hardening an existing auth layer

Don't use for:

• Authorization / RBAC (permissions after authentication)
• Specific framework setup (use express, nest, nextjs)

Critical Patterns