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LOADLoad BalancerWS SWS Server 1WS SWS Server 2PRESPresence ServiceREDIRedisNOTINotificationsCASSCassandra DB

Real-time Chat System

A real-time chat system facilitates instant messaging between users. It uses persistent connections (like WebSockets) to deliver messages with low latency. The architecture must be highly scalable to support millions of concurrent connections and messages per second.

Key Components

WebSocket Server
Load Balancer
User Presence Service
Message History Database (Cassandra)
Cache (Redis)
Notification Service

Design Challenge

Maintaining massive persistent connections and ensuring low-latency message delivery without dropping messages.

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