Security

Security is not a feature; it is the foundation. Master AuthN vs AuthZ, the endless Session vs JWT debate, and how to define against the OWASP Top 10.

What you will learn

  • Decide between Stateful (Session) and Stateless (JWT) Authentication
  • Understand the trade-off: Instant Revocation vs Infinite Scale
  • Differentiate RBAC vs ABAC
  • Defend against the titans: SQL Injection, XSS, and CSRF

A system that is fast, scalable, and well-designed still fails completely if it leaks user data. Security is not a layer you add after the architecture is done — it shapes the architecture itself. The patterns in this chapter are the minimum baseline for any production system that handles user identity or sensitive data.

These two acronyms look alike but solve different problems.

How does the server remember the user?

  1. User logs in.
  2. Server generates a random ID (sess_123).
  3. Server writes sess_123 -> UserID: 5 in its database (Redis).
  4. Server gives cookie sess_123 to User.
  • Pros: Control. You can revoke a session instantly. (Delete it from Redis).
  • Cons: Scale. Every single request requires a database lookup ("Is this session valid?").
  1. User logs in.
  2. Server creates a JSON object: { "userId": 5, "role": "admin", "expires": "tomorrow" }.
  3. Server Cryptographically Signs it (using a secret key) so it can't be forged.
  4. Server gives this token to User.

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