zlacker

With a realistic, that is, not 100% reliable, queue you can have either "at most once" or "at least once" delivery anyway. "Exactly once" can't be guaranteed.

So a duplicate message should be processed as normal anyway, e.g. by deduplication within a reasonable window, and/or by having idempotent operations.

>>nine_k+(OP)
Yes, it depends on the workload. Idempotency is typically always a good idea, but sometimes the operation itself is very expensive in terms of time, resources, and/or money. I have also seen people try to update the message when writing it back(with checkpoint information and etc) for long running processes. A slew of issues, including at least once delivery, can cause workflow bifurcation. Deduplication via FIFO _can_ help mitigate this, but it has a time window that needs to be accounted for. Once you start managing your own deduplication I'd say it has moved past trying to go databaseless.