JWT vs Sessions: Stateless or Server State?
JWTs are self-contained tokens verified by signature without server lookup; sessions store state server-side and reference it with a cookie.
JWT auth puts claims in a signed token the server validates statelessly, which scales horizontally without shared session storage but makes immediate revocation hard. Session auth keeps state in a store (memory, Redis, DB) referenced by a session ID cookie, giving easy revocation and small cookies at the cost of a lookup and shared storage. JWT favors statelessness; sessions favor control and revocation.
| JWT | Sessions | |
|---|---|---|
| State | Stateless (in token) | Server-side store |
| Revocation | Hard (until expiry) | Easy (delete session) |
| Scaling | No shared store | Needs shared store |
| Payload size | Larger token | Small cookie |
| Best for | APIs, microservices | Web apps, easy logout |
Tradeoffs
JWTs suit stateless APIs and service-to-service calls where you want to avoid a central session store; keep them short-lived and pair with refresh tokens to mitigate weak revocation. Sessions suit classic web apps needing instant logout, easy invalidation, and small cookies, accepting a shared store like Redis. Many systems use sessions for browser apps and JWTs for APIs.
In CI
Auth integration tests should exercise expiry and revocation paths. Store signing keys/secrets in the CI secret store. On managed runners, mask secrets and avoid baking keys into images.
The verdict
Stateless APIs and microservices where avoiding a session store matters: JWT (short-lived, with refresh). Web apps needing instant logout and simple revocation: server-side sessions. A hybrid - sessions for browsers, JWTs for APIs - is common and avoids each model's main weakness.