Chat / Messaging System
hardOpen designVery commonly asked~45 minHLD roundBar raiserSenior / SDE-3MetaGoogleAmazonMicrosoftPhonePeQueues & AsyncStorage & Data ModellingConsistency & Consensus
The question, as asked
“Design a messaging app like WhatsApp. Start with one-to-one chat and we'll go from there.”
Your answer, first
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Worked answer in progress
This one is listed because it comes up constantly — the three-depth answer, follow-ups and red flags are being written. Attempt it above anyway; that part works, and the guides below cover the ground the model answer will.