Scaling Redis for 10M Concurrent WebSockets

Managing millions of open WebSocket connections is an architectural challenge, particularly in serverless or containerized environments. Standard stateful connections demand massive RAM layouts. By introducing Redis Pub/Sub as an event coordination bus, we distribute session states cleanly.

WebSocket Mesh Topology

[Client Sessions]  -->  [Next.js Socket Nodes (Scale)]
                              |
                              +--> [Redis Sentinel / Cluster Bus]
                                         |
                                         +--> [Pub/Sub Ledger Streams]

Memory Footprint Reductions

Each WebSocket handle normally requires ~25KB of system memory buffer in Node.js. By pooling sockets and delegating heartbeat registers directly to a shared Redis cluster hash mapping, we cut local socket RAM overhead by up to 60%.

Code Setup: Redis connection pooling

import Redis from "ioredis";

const redisPool = new Redis.Cluster([
  { host: "redis-node-1", port: 6379 },
  { host: "redis-node-2", port: 6379 }
], {
  scaleReads: "slave",
  maxRedirections: 16
});