Why it matters

Chat is common design. Understanding shapes realtime apps.

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The architecture

WebSocket for realtime.

Message queue for async.

Persistent store for history.

Chat architectureWebSocketrealtimeMessage queuedelivery + retryPersistent storehistory + searchSignal Protocol for E2E encryption; complex but standard for private chat
Chat design.
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How it works end to end

Delivery guarantees: at-least-once with dedup.

Ordering: per-conversation.

Read receipts + typing indicators.

End-to-end encryption: Signal Protocol.