SQS Message Handling and Visibility Timeout

Reliably processing messages from an SQS queue requires understanding how visibility timeouts work, how to handle failures gracefully, and how to design consumers that are idempotent. In this lesson, we dive deep into the message lifecycle and the patterns that make SQS-based systems production-ready.

---

The Message Lifecycle

Every message in SQS moves through a defined lifecycle:

1. Sent — the producer sends the message to the queue
2. Available — the message is sitting in the queue, waiting to be received
3. In-flight — a consumer has received the message, and it is temporarily invisible to other consumers
4. Deleted — the consumer successfully processed the message and deleted it
5. Re-available — if the consumer fails to delete the message before the visibility timeout expires, it becomes visible again

[Sent] ——> [Available] ——> [In-flight] ——> [Deleted]
                              |
                              v  (visibility timeout expires)
                          [Re-available]

---

Understanding Visibility Timeout

The visibility timeout is the period during which a message, once received by a consumer, is invisible to all other consumers. This prevents multiple consumers from processing the same message simultaneously.

How It Works