Design a chat messaging system
Quick Overview
This question evaluates the ability to design scalable, reliable real-time messaging systems, examining competencies in distributed systems, message delivery semantics (sent/delivered/read), offline store-and-forward, multi-device history synchronization, and conversation ordering.
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Feb 25, 2026, 12:00 AM
Software Engineer
Onsite
System Design
1
0
Design a chat system similar to WhatsApp/Messenger.
Requirements:
- 1:1 and group chats.
- Send/receive messages in real time when online; store-and-forward when offline.
- Delivery states (sent/delivered/read) are desirable.
- Support message history sync across devices.
- Handle ordering within a conversation.
Out of scope: end-to-end encryption details, media pipeline.
Solution
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