JWT is stateless — all state in the token, trivial horizontal scaling, but revocation requires a blacklist. Sessions are stateful — state in Redis, instant revocation by deleting the session, but require a shared store across instances. Use JWT for APIs and SPAs; use sessions for server-rendered apps and compliance requirements.
The fundamental trade-off is statefulness. JWT externalizes state to the client — the server has no record of issued tokens. Sessions centralize state in a shared store — every instance can revoke a session immediately by deleting it.
Choose JWT for: stateless horizontal scaling, microservices that verify tokens independently, SPAs and mobile clients, short-lived tokens (15m) with refresh token rotation.
Choose sessions for: server-rendered apps (Next.js SSR), immediate logout as a hard requirement, B2B apps where admins must terminate any session instantly, HIPAA and SOC2 compliance requiring auditable active sessions.
JWT limitation: revocation requires a Redis blacklist — short expiry and refresh rotation are the primary mitigations.
Session limitation: requires sticky sessions or a shared Redis store — adds operational complexity.
Hybrid approach: use sessions for browser clients and JWT for API/mobile clients with a guard that accepts either.