System Design Study

Real-time Chat / Messenger

Design the client-side system architecture for a real-time messaging application (like WhatsApp Web or Slack). Focus on connection protocols, sync consistency, and offline local cache sync.

Step Budget5:00

Draft Your Answer Notes

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Take a few minutes to write down your initial ideas on the left first. When you are ready, reveal the verified model architecture.

✨ Senior Evaluator Notes

Evaluate if they explain sequence clocks (e.g., Vector clocks) to handle sync issues under connectivity gaps.

⚠️ Common Pitfalls

Not handling gaps upon connection reconnects (leading to lost messages).
Sending huge messages frame-by-frame instead of structuring lightweight event packets.