90% of developers pick the wrong authentication method.
Then spend months patching the consequences.
JWT, Session, OAuth 2.0, API Keys - they're not interchangeable. Each one solves a different problem.
Here's the breakdown every backend engineer should know 👇
🔹 𝗦𝗲𝘀𝘀𝗶𝗼𝗻
Server creates a session on login, stores it in Redis/DB, returns session ID via cookie.
→ Stateful. Easy to revoke. Best for traditional web apps with a single backend.
→ Weakness: doesn't scale across services without a shared store.
🔹 𝗝𝗪𝗧
Server signs a token with claims (user, expiry, scope). Client sends it on every request.
→ Stateless. Scales infinitely. Best for microservices, SPAs, mobile apps.
→ Weakness: hard to revoke before expiry, payload is visible by default.
🔹 𝗢𝗔𝘂𝘁𝗵 𝟮.𝟬
User grants third-party apps limited access via an authorization server.
→ Mixed state. Industry standard for delegation. Best for "Login with Google," GitHub access, third-party integrations.
→ Weakness: complex to implement correctly - auth code, PKCE, client credentials, device flows.
🔹 𝗔𝗣𝗜 𝗞𝗲𝘆𝘀
Static long-lived secret tied to a service or developer account.
→ Stateful. Simple to rotate. Best for server-to-server APIs, SDKs, internal services.
→ Weakness: no user identity, no expiry by default. Leaked keys are dangerous.
The rule:
→ Web app, one backend → Session
→ Microservices, mobile, SPA → JWT
→ Third-party access → OAuth 2.0
→ Server-to-server → API Keys
Picking the wrong one isn't a bug. It's a security incident waiting to happen
Which one do you use most?
Obs: All Right to Original Creator @Rocky Bhatia - Linkdin Profile
#Backend #SystemDesign#Authentication #WebDevelopment #Engineering
