Session Management with Redis — Interactive Architectural Guide

USER BROWSER

Client

Browser Cookie Jar ANONYMOUS

Cookie: sid=

Flags: HttpOnly; Secure

[BROWSER] Ready to send HTTP requests...

Requests Sent 0 reqs

401 Rejections 0

LOAD BALANCER

L7 Proxy

Routing Policy ROUND ROBIN

Sticky Sessions DISABLED

Active Target Server A

Upstream pool: 2 healthy nodes

APP SERVER A

Node 1

Local RAM Session Map LOCAL ONLY

Empty {}

Idle — listening on :8080

APP SERVER B

Node 2

Local RAM Session Map LOCAL ONLY

Empty {}

Idle — listening on :8080

REDIS SESSION STORE

Shared KV

HASH KEY: sess:xyz STANDBY

(nil) — No active session hash

Key TTL Countdown N/A

127.0.0.1:6379> Waiting for commands...

1. The Local Session Problem

Before Redis, servers stored sessions in their own local process memory. When a user logs in, the Load Balancer routes the request to App Server A, which saves the session locally and returns Set-Cookie: sid=local_123.