Payment events must be processed exactly once, in strict order. Which SQS configuration delivers both guarantees?
A.A standard queue with a short visibility timeout
Standard queues can deliver duplicates — visibility timeout doesn't prevent that.
B.A FIFO queue — message groups preserve ordering and content/dedup-ID deduplication prevents repeats
Correct. FIFO = order + exactly-once.
C.A standard queue with long polling
Long polling improves efficiency, not ordering/dedup.
D.SNS fan-out to a standard queue
SNS doesn't add ordering to a standard queue.
Why this answer
Only FIFO queues guarantee ordering (per message group ID) and exactly-once delivery via deduplication (content-based or explicit dedup IDs). Standard queues are at-least-once with best-effort ordering — duplicates and reordering are expected.
Correct answer: B · Last reviewed 2026-10-27
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