SQS Is Delivering the Same Message Twice. Is the Queue Broken?
Consumers occasionally process the same SQS message twice, causing double charges. A teammate says switch everything to FIFO. Defend the real fix.
the decision you defend
Your workers sometimes process the same SQS message twice, leading to duplicate charges and emails. A teammate says standard SQS is broken and wants to move everything to FIFO. What is actually happening, and what do you do?
the situation
A small fraction of jobs in your queue-driven system run twice. Because each job charges a card and sends a receipt, the duplicates show up as double charges and duplicate emails to customers.
context
Workers poll a standard SQS queue, do work that can take a couple of minutes, then delete the message. The queue visibility timeout is set to thirty seconds. There is no dead-letter queue and the processing has no dedup or idempotency key. A teammate concluded that standard SQS is unreliable and wants to migrate every queue to FIFO.
How this challenge works
Take a position on the decision above and defend it. A senior-engineer AI will push back over up to 5 rounds. When you are done, you are scored against a verified rubric so you can see exactly what a complete answer covers - these are learning prompts, not gotchas.