Authentication is hard. Doing it wrong leads to data breaches. Here is how to choose the right strategy.

1. Session-Based (Stateful)

How it works: Server creates a session ID, stores it in DB/Memory, and sends it as a Cookie.

Pros: Easy to revoke (delete session). Secure (HttpOnly cookies).

Cons: Harder to scale (sticky sessions or Redis required).

2. JWT (Stateless)

How it works: Server signs a token (JSON Web Token) with a secret. Client stores it. Server verifies signature.

Pros: Scalable (no DB lookup). Good for microservices.

Cons: Hard to revoke (need blacklisting). Token size.

3. OAuth 2.0 (Social Login)

How it works: "Log in with Google". You trust a third party to verify identity.

Flow:

  1. User clicks "Login".
  2. Redirect to Google.
  3. User approves.
  4. Google redirects back with code.
  5. Server exchanges code for token.

Security Best Practices

  • Always use HTTPS.
  • Store passwords using bcrypt/argon2. Never plain text.
  • HttpOnly Cookies are safer than LocalStorage for tokens (XSS protection).