JSON Web Tokens (JWTs) are often praised for their simplicity and scalability in stateless authentication. They allow clients to authenticate once and use the token for subsequent requests without needing to hit the database again. Sounds great, right? Well, not always. While JWTs have their place, they might not be the best choice in some situations. Let’s break down five reasons why JWTs could be a poor fit for your authentication needs.
1. Revocation is a Nightmare
One of the biggest challenges with JWTs is that once a token is issued, you can’t easily revoke it until it expires. Unlike session-based authentication, where you can simply delete a session from your database, JWTs are stateless and self-contained.
Imagine an employee leaves a company, but their JWT is still valid for another hour. There’s no easy way to invalidate it immediately unless you implement token blacklisting, which ironically brings back statefulness—the very thing JWTs were supposed to eliminate.
Alternative: A session-based authentication system allows instant revocation by deleting a session record from the server.
2. Security Risks with Long-Lived Tokens
JWTs often include expiration times (e.g., one hour, one day), but if a token is compromised before it expires, an attacker can use it until it naturally expires. This is particularly risky in scenarios where long-lived refresh tokens are used.
Sure, you can mitigate this by using short expiration times, but that increases the frequency of re-authentication, adding friction for users.
Alternative: Server-side session tokens can be invalidated immediately if a security breach is detected.
3. JWTs Are Large and Inefficient
A typical JWT contains three parts:
- Header (e.g., algorithm type)
- Payload (e.g., user details, permissions)
- Signature (for verification)
This structure, while compact in theory, often results in bloated tokens because of extra metadata and Base64 encoding. A simple user session might balloon into a 300-600 byte token, compared to a lightweight session ID (often just 16-32 bytes).
The larger the token, the more data needs to be sent with every request, which can slow down network performance, especially on mobile devices or in high-traffic applications.
Alternative: A simple session ID stored in a secure, encrypted cookie is much smaller and more efficient.
4. No Built-In Session Management
JWTs are stateless, which means there’s no automatic session tracking or lifecycle management. If a user logs in on multiple devices, there’s no way to track active sessions or selectively log out specific sessions.
If you want features like multi-device session tracking, forced logouts, or user session analytics, you’ll have to build that logic yourself—often by reintroducing state in a database, which defeats the purpose of using JWTs.
Alternative: Traditional session-based authentication keeps track of sessions on the server, making it easier to manage logins across multiple devices.
5. Signature Verification Adds Overhead
JWTs require signature verification on every request to ensure they haven’t been tampered with. This cryptographic verification, while necessary for security, adds extra processing overhead compared to a simple database lookup for a session.
For high-performance applications, especially those handling thousands of requests per second, this additional computation can become a bottleneck.
Alternative: A session store (e.g., Redis or an SQL database) allows quick lookups without the need for constant cryptographic validation.
So, When Should You Use JWTs?
Despite these drawbacks, JWTs still shine in certain use cases:
→ Microservices Authentication – Since JWTs are self-contained, they can be passed between microservices without needing centralized authentication lookups.
→ Third-Party API Authorization – JWTs work well for OAuth and API access, where stateless authentication is an advantage.
→ Short-Lived Tokens – If you’re issuing short-lived tokens and don’t require revocation, JWTs can work well.
However, if your application requires session management, revocation control, or efficiency in network performance, traditional session-based authentication is often the better choice.
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