How to design a chat application architecture

· Category: System Design

Short answer

Use WebSockets for real-time delivery, a message queue for reliability, and a database for persistence. Shard conversations for scalability. For related scaling techniques, see how caching improves system performance. For content delivery, see how cdns speed up content delivery.

Steps

  1. Establish WebSocket connections between clients and servers
  2. Use a message queue to buffer messages during spikes
  3. Store messages in a database with conversation-based sharding
  4. Implement presence and read receipts
  5. Add push notifications for offline users

Tips

  • Use connection multiplexing to handle millions of concurrent sockets
  • Keep recent messages in cache for fast history loading
  • For choosing infrastructure, see how to choose a cloud provider