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System design

Chat App (e.g. Messenger)

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Question

Design a browser-based 1:1 chat application that supports text messages, real-time delivery, optimistic sending, offline queuing, delivery states, and reconnect catch-up. Assume one active tab per account for the core design.

Group conversations, rich media, calls, search, push notifications, end-to-end encryption, and coordinated multi-tab ownership are potential follow-ups rather than core requirements.

Abstract two-pane chat interface with a conversation list, selected thread, and message composer

Real-life examples

These products demonstrate the messaging, delivery-state, and conversation-navigation patterns in scope.

    Chat App (e.g. Messenger) | Front End System Design Question