JWT vs Session Tokens: When to Use Each

Table of Contents

• How Sessions Work
• How JWTs Work
• Key Tradeoffs
• When to Use Sessions
• When to Use JWTs
• The Hybrid Approach

How Sessions Work

1. User logs in → server creates a session record in the database
2. Server sends a session_id cookie to the client
3. On every request, the server looks up session_id in the DB
4. If found and valid, the user is authenticated

Pros: Instant revocation, simple to implement, small cookie Cons: Every request hits the DB, hard to scale horizontally

How JWTs Work

1. User logs in → server creates a signed JWT with user claims
2. JWT is sent to the client
3. On every request, the server verifies the signature — no DB lookup
4. Claims in the payload are trusted

Pros: Stateless, scalable, works across microservices Cons: Can't revoke until expiry, payload is visible (just Base64)

Key Tradeoffs

When to Use Sessions

• Traditional web app with server-side rendering
• Need to revoke sessions instantly
• Single-server deployment

When to Use JWTs

• Distributed microservices architecture
• Mobile apps where cookies are cumbersome
• Cross-domain authentication (SSO)

The Hybrid Approach

Most modern apps use both:

• Refresh token = long-lived, stored as httpOnly cookie, stored in DB (revocable)
• Access token = short-lived JWT (15 min), verified in-memory, no DB call