Amazon Web Services · Associate
AWS Certified Developer - Associate
If the function takes longer than the visibility timeout, the message becomes visible again and another invocation picks it up while the first is still processing: guaranteed duplicates. AWS recommends a visibility timeout ≥ 6× the function timeout. The module computes and validates it.
By default, if the function fails the whole batch goes back to the queue, including already processed messages. With function_response_types = ["ReportBatchItemFailures"] the function returns only the failed IDs. In Azure and GCP acks are per message, so this problem doesn't exist in the same way.
When moving a message to the DLQ, SQS keeps the original enqueue timestamp (in FIFO it resets). If the DLQ has the same retention as the source queue, messages can vanish from the DLQ almost immediately. Set the DLQ retention longer than the source (the module uses the maximum, 14 days).
scaling_config.maximum_concurrency limits how many concurrent instances of the function the queue can invoke. It's an event source mapping setting, independent of the function's reserved concurrency and free of charge, and it keeps one queue from using all of the reserved concurrency or the account's concurrency quota. Note: the reserved concurrency must be greater than or equal to the sum of the maximums of all the function's event sources; otherwise Lambda might throttle your messages.
Letra Chica