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Design Facebook Messenger

System Design · Uber · Medium

Design a real-time messaging platform that powers 1:1 and small-group conversations across mobile and web clients. Users expect instant message delivery on every device, yet the system's backbone must be a strictly ordered, durable conversation history that survives crashes, reconnects, and cross-device transitions. Presence indicators, read receipts, and push notifications operate as fast, best-effort layers built atop this authoritative log, not as independent sources of…

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