User authentication is an architectural decision that affects security, scalability, and user experience. JWT and sessions are the dominant approaches.
Session-based authentication
Sessions store state on the server (memory, Redis, database). The client receives a session ID cookie. Easy to implement, sessions can be invalidated instantly, and there's no risk of long-lived stolen tokens. However, it requires shared storage between instances and scales worse in distributed architectures.
JWT (JSON Web Tokens)
JWT encodes user information in a signed token stored by the client (localStorage, cookie). It requires no server state, making horizontal scaling easy. Ideal for RESTful APIs, microservices, and mobile applications.
JWT disadvantages
JWT tokens cannot be invalidated before expiration (without a blacklist, which reintroduces state). Token size can be large. If the signing key is compromised, all tokens are vulnerable.
Practical recommendations
Use sessions for traditional server-side rendered web applications needing immediate invalidation. Use JWT for public APIs, mobile apps, microservices, and stateless server scenarios.
Consider using refresh tokens with JWT to balance security and user experience. The access token (short-lived) + refresh token (long-lived) combination is industry standard.
Authentication is your application's front door. At Vynta, we design robust and secure authentication systems tailored to your architecture.