Stateful vs Stateless: Where the Session Lives

Sun, 06 Sep 2026 09:51:46 +0900

Overview

This comparison covers whether a server or protocol retains session state between requests, or treats every request as a fully self-contained unit with no memory of prior ones. The choice determines how you scale, fail over, and route traffic across instances.

Comparison Diagram

Comparison Table

Aspect	Stateful	Stateless
Request context	Server retains prior interaction data across requests	Each request carries all context needed to process it
Session storage	Held in server memory or local session store	None on server; state lives in client token or database
Routing requirement	Requests must reach the same server (sticky sessions)	Any server instance can handle any request
Scaling model	Vertical or sticky-session horizontal scaling only	Trivial horizontal scaling, load balance freely
Failure recovery	Server crash loses in-memory session unless replicated	Server crash has no session impact, retry hits any node
Client design	Client can be thin, server tracks progress	Client or token must resend full context each call
Typical examples	Database connections, WebSocket sessions, FTP	REST APIs, HTTP with JWT, DNS lookups

Key Differences

Stateful servers keep session memory; stateless servers keep none between calls
Stateless systems need no sticky routing, simplifying load balancers
Stateful failover requires session replication to avoid data loss
Stateless designs push state into the client or token instead of the server
Horizontal scaling is near-free for stateless architectures

When to Use Each

Stateful

Stateful-Stateless on IT Comparison

Stateful vs Stateless: Where the Session Lives

Overview

Comparison Diagram

Comparison Table

Key Differences

When to Use Each