Does a FIFO queue make a business action always run exactly once?
Answer out loud or in your head first, then compare.
Answer
It doesn't give such a general guarantee for the whole system. FIFO can order messages within a group and limit duplicate sends within a certain window. It doesn't automatically put our database and someone else's API into one transaction.
A program can create a request and then lose the connection before acknowledging the message. The next attempt shouldn't create a second request. We still need an operation identifier and a check of its effect. Cloudflare Queues allows redelivery, and you shouldn't assume publication order is preserved. SQS Standard allows duplicates too. When choosing, I read the guarantees of the specific service, not just the phrase “exactly once” in a description.
Why it matters: Tests understanding of the limits of guarantees, without learning a slogan.
Possible follow-ups: Within what scope does FIFO keep order? What identifies the same action?
How did it go? Be honest — “Not yet” puts the question on your review list.
Start with
- E-P01 · What is cloud computing? — AWS, Cloudflare and infrastructure
- E-P03 · What is Cloudflare, and what is it for? — AWS, Cloudflare and infrastructure
- E-P04 · How does Cloudflare differ from AWS? — AWS, Cloudflare and infrastructure
Further reading
- Cloudflare Queues: Delivery guarantees(opens in a new tab)Docs; accessed 22.10.2026. At-least-once delivery and deduplicating side effects.
- AWS: Exactly-once processing in Amazon SQS(opens in a new tab)Docs; accessed 22.10.2026. The scope of FIFO deduplication; not a global transaction with an external side effect.