Fundamentals Of Backend Engineering Hussein Nasser Updated May 2026

| Feature | Stateless | Stateful | | :--- | :--- | :--- | | | Stored client-side (JWT) or in external cache (Redis) | Stored in server memory | | Scaling | Easy (add any instance) | Hard (requires sharding or sticky sessions) | | Resilience | High (server dies, no data loss) | Low (server dies, session dies) | | Use case | REST APIs, Serverless | WebSockets, Gaming, File uploads |