System Design · Whatnot · Medium
Design a real-time chat service comparable to WhatsApp. It must support both direct one-to-one conversations and group chats. For users whose clients are currently connected, incoming messages should be delivered with very low latency. If a user is offline or disconnected, messages must remain safe and be delivered or retrieved when that user reconnects. The scope is limited to core messaging rather than every auxiliary social feature. Message persistence is required. Online…
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