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WebSockets & Realtime Systems Programming · Lesson

Message Acknowledgement and Delivery Guarantees

Ensure messages are not silently lost by adding acknowledgements, retries, and idempotency to reach reliable delivery guarantees.

Messages Can Vanish

A message can be lost if the socket drops mid-send, the server crashes, or the client reloads before processing. Without acknowledgements, neither side knows it happened.

Delivery Guarantee Levels

Three common guarantees:

  • At-most-once: may lose, never duplicate
  • At-least-once: never lose, may duplicate
  • Exactly-once: never lose, never duplicate (hardest)

All lessons in this course

  1. Handling Disconnections and Reconnects
  2. Robust Error Propagation and Recovery
  3. Heartbeats and Keep-Alives
  4. Message Acknowledgement and Delivery Guarantees
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