When building secure APIs, JWT (JSON Web Token) is one of the most popular authentication methods. It’s lightweight, stateless, and easy to integrate. But JWT has one common problem: once a token is issued, it remains valid until it expires—even if the user logs out.
This creates a security gap where someone with access to the token can still make requests until it naturally expires.
Let’s explore how to fix this using Redis.
The Problem: Token Still Valid After Logout
JWT works without server-side session tracking. Once a token is signed, the server doesn’t store it—validation is done by checking the signature.
That means:
- If a user logs out, the token doesn’t automatically become invalid.
- If an attacker steals or copies the token, they can use it until expiration.
The Solution: Using Redis as a Blacklist
To solve this, we can introduce a token blacklist mechanism with Redis.
Here’s how it works:
When the user logs out, store the token in Redis with an expiration time matching the JWT expiry.
On every API request, check if the token exists in Redis.
- If yes → reject the request (Unauthorized or Illegal Access).
- If no → proceed with normal JWT validation.
This way, even if someone has a stolen token, it won’t work after the user logs out.
Benefits of This Approach
Immediate logout → Users are logged out instantly, not just after JWT expiry.
Extra security → Protects against token theft and replay attacks.
*Scalable *→ Redis is fast and works well with distributed systems.
Conclusion
JWT is powerful, but without proper logout handling, it can leave your application vulnerable. By integrating Redis as a blacklist, you can ensure better session control and stronger security for your applications.
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