#5Medium
Design Facebook Messenger or WhatsApp
Asked by:FacebookUberTikTokAmazon
Recommended Solutions from the Web
Good overview
https://hayksimonyan.substack.com/p/system-design-interview-design-whatsapp
Good solution
https://medium.com/%40m.romaniiuk/system-design-chat-application-1d6fbf21b372
Real time chat
https://medium.com/%40ishwarya1011.hidkimath/system-design-design-a-chat-system-e0056fb093d1
Great video
https://www.youtube.com/watch?v=-3Ge8EooS3g
Key Details & Edge Cases You Should Know
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How do you ensure low-latency message delivery (< 100ms) across millions of users?
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What communication protocol will you use (long polling, WebSockets)?
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How do you handle offline users and guarantee eventual delivery?
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Where do you store messages - do you persist all, or support auto-deletion?
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How will you implement push notifications on iOS/Android reliably?
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How do you support multi-device sync (message states consistent across devices)?
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How will you manage group messaging - fan-out on write vs fan-out on read?