We actually already use the DeadLetterQueues in our service at the moment, but these are when failed SQS deliveries happen, then they get replicated to the DLQ.

I am more interested in diagnosing successful SQS deliveries after the fact, to see what the payloads were in case there was a downstream problem.

It seems that SQS deliveries that don't get a 200 response from our service go to the DLQ, but those that get a successful 200 disappear into the ether.