Would changing an SQS standard queue to FIFO eliminate duplicate external side effects when a worker crashes after a successful API call but before deleting the message? Find current official AWS sources. Produce a short adoption decision and compare send deduplication, ordering, redelivery and application idempotency. Include the documented deduplication window and explicit limits of any exactly-once claim.
10/4/2026, 11:41:43 PM · llm:deepseek:deepseek-v4-flash
> ⚠ Low confidence — Only source excerpts are delivered; complete synthesis and per-assertion support remain unverified. Evidence assessment: the final assessment does not establish a complete supported answer for every requested part within budget. Treat this as provisional.
Source excerpts only. The draft is withheld as a conclusion; complete synthesis is unverified. Qualifying source excerpts are quoted below. Research targets are topics to investigate, not established conclusions.
Research target 1
Requested topic (unverified): “Does changing an SQS standard queue to FIFO eliminate duplicate external side effects when a worker crashes after a successful API call but before deleting the message?”
- “A FIFO consumer can still execute business code again after its visibility timeout expires or after it commits an effect and fails before deleting the message.”
- “AWS calls the FIFO feature “exactly-once processing,” but its documented mechanism does not make your database update and DeleteMessage one atomic operation.”
Research target 2
Requested topic (unverified): “What is the documented deduplication window for SQS FIFO queues according to current official AWS sources?”
- “It ensures that within a 5-minute deduplication window, only one instance of a message with the same deduplication ID is processed and delivered.”
Research target 3
Requested topic (unverified): “What are the explicit limits of any exactly-once claim for SQS FIFO queues according to current official AWS sources?”
- “AWS calls the FIFO feature “exactly-once processing,” but its documented mechanism does not make your database update and DeleteMessage one atomic operation.”
- “There is no distributed transaction joining an arbitrary database or external API to SQS deletion.”
Research target 4
Requested topic (unverified): “How does SQS FIFO send deduplication work according to current official AWS sources?”
- “MessageDeduplicationId is a token used only in Amazon SQS FIFO queues to prevent duplicate message delivery.”
- “If Amazon SQS has already accepted a message with a specific deduplication ID, any subsequent messages with the same ID will be acknowledged but not delivered to consumers.”
Research target 5
Requested topic (unverified): “How does SQS FIFO ordering work according to current official AWS sources?”
- “FIFO queues add producer-side deduplication and strict ordering within each message group.”
Research target 6
Requested topic (unverified): “How does SQS FIFO redelivery work according to current official AWS sources?”
- “Consumer redelivery: one queued message is received again after failed or incomplete settlement.”
Research target 7
Requested topic (unverified): “How does application idempotency relate to SQS FIFO queues according to current official AWS sources?”
- “Use FIFO to control queue-introduced duplicates and per-group order; use application idempotency to control repeated effects.”
- “Long-lived API idempotency requires a durable application record, not just FIFO's recent-send memory.”
Research target 8
Requested topic (unverified): “What is the short adoption decision for changing an SQS standard queue to FIFO to address duplicate external side effects when a worker crashes after a successful API call but before deleting the message?”
- “Use FIFO to control queue-introduced duplicates and per-group order; use application idempotency to control repeated effects.”
- “Keep the latter order and make the effect idempotent.”
Excerpts establish source grounding, not factual truth, entailment or whole-paper coverage. Support and coverage are estimates, not certification of a complete answer. Source statements may be wrong or conflicting. Draft conclusions are withheld; inspect the original text and obtain further review. Payment states remain in the separate receipt.
Next steps to complete this research
These are suggested follow-up steps; this run has not performed them. They do not change the recorded evidence or payment state.
- The model flagged differing source statements; that assessment is not independently verified. Compare the original passages and revisions, then ask the document owner which policy or result applies. The model's preferred source does not resolve a conflict.
Evidence ledger — recorded source excerpts
Research targets are unverified topics. Coverage is an estimate of excerpt support, not proof of entailment, factual truth or a complete answer.
Requested topic (unverified): “Does changing an SQS standard queue to FIFO eliminate duplicate external side effects when a worker crashes after a successful API call but before deleting the message?”
90% estimated“A FIFO consumer can still execute business code again after its visibility timeout expires or after it commits an effect and fails before deleting the message.” [S1] SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee
“AWS calls the FIFO feature “exactly-once processing,” but its documented mechanism does not make your database update and DeleteMessage one atomic operation.” [S1] SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee
Requested topic (unverified): “What is the documented deduplication window for SQS FIFO queues according to current official AWS sources?”
90% estimated“It ensures that within a 5-minute deduplication window, only one instance of a message with the same deduplication ID is processed and delivered.” [S4] Using the message deduplication ID in Amazon SQS
Requested topic (unverified): “What are the explicit limits of any exactly-once claim for SQS FIFO queues according to current official AWS sources?”
60% estimated“AWS calls the FIFO feature “exactly-once processing,” but its documented mechanism does not make your database update and DeleteMessage one atomic operation.” [S1] SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee
“There is no distributed transaction joining an arbitrary database or external API to SQS deletion.” [S1] SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee
Requested topic (unverified): “How does SQS FIFO send deduplication work according to current official AWS sources?”
80% estimated“MessageDeduplicationId is a token used only in Amazon SQS FIFO queues to prevent duplicate message delivery.” [S4] Using the message deduplication ID in Amazon SQS
“If Amazon SQS has already accepted a message with a specific deduplication ID, any subsequent messages with the same ID will be acknowledged but not delivered to consumers.” [S4] Using the message deduplication ID in Amazon SQS
Requested topic (unverified): “How does SQS FIFO ordering work according to current official AWS sources?”
60% estimated“FIFO queues add producer-side deduplication and strict ordering within each message group.” [S1] SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee
Requested topic (unverified): “How does SQS FIFO redelivery work according to current official AWS sources?”
60% estimated“Consumer redelivery: one queued message is received again after failed or incomplete settlement.” [S1] SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee
Requested topic (unverified): “How does application idempotency relate to SQS FIFO queues according to current official AWS sources?”
60% estimated“Use FIFO to control queue-introduced duplicates and per-group order; use application idempotency to control repeated effects.” [S1] SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee
“Long-lived API idempotency requires a durable application record, not just FIFO's recent-send memory.” [S1] SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee
Requested topic (unverified): “What is the short adoption decision for changing an SQS standard queue to FIFO to address duplicate external side effects when a worker crashes after a successful API call but before deleting the message?”
70% estimated“Use FIFO to control queue-introduced duplicates and per-group order; use application idempotency to control repeated effects.” [S1] SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee
“Keep the latter order and make the effect idempotent.” [S1] SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee
What if a source were missing?
Temporarily leave out one source to see which research targets retain excerpts in this report.
Showing the original excerpt ledger.
Does changing an SQS standard queue to FIFO eliminate duplicate external side effects when a worker crashes after a successful API call but before deleting the message?
2 recorded excerpts remain.
Inspect remaining excerpts
“A FIFO consumer can still execute business code again after its visibility timeout expires or after it commits an effect and fails before deleting the message.”
S1 · oneuptime.com · SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee · version e4200a54840f3c862fa849e1b48e2724d9195024025f56e0659566501adc7d0e
“AWS calls the FIFO feature “exactly-once processing,” but its documented mechanism does not make your database update and DeleteMessage one atomic operation.”
S1 · oneuptime.com · SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee · version e4200a54840f3c862fa849e1b48e2724d9195024025f56e0659566501adc7d0e
What is the documented deduplication window for SQS FIFO queues according to current official AWS sources?
1 recorded excerpt remain.
Inspect remaining excerpts
“It ensures that within a 5-minute deduplication window, only one instance of a message with the same deduplication ID is processed and delivered.”
S4 · amazon.com · Using the message deduplication ID in Amazon SQS · version ebcc5fd648fd4a60b2f982a6ed31159a3fb7c3689cb1f171ab45c907ddde454a
What are the explicit limits of any exactly-once claim for SQS FIFO queues according to current official AWS sources?
2 recorded excerpts remain.
Inspect remaining excerpts
“AWS calls the FIFO feature “exactly-once processing,” but its documented mechanism does not make your database update and DeleteMessage one atomic operation.”
S1 · oneuptime.com · SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee · version e4200a54840f3c862fa849e1b48e2724d9195024025f56e0659566501adc7d0e
“There is no distributed transaction joining an arbitrary database or external API to SQS deletion.”
S1 · oneuptime.com · SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee · version e4200a54840f3c862fa849e1b48e2724d9195024025f56e0659566501adc7d0e
How does SQS FIFO send deduplication work according to current official AWS sources?
2 recorded excerpts remain.
Inspect remaining excerpts
“MessageDeduplicationId is a token used only in Amazon SQS FIFO queues to prevent duplicate message delivery.”
S4 · amazon.com · Using the message deduplication ID in Amazon SQS · version ebcc5fd648fd4a60b2f982a6ed31159a3fb7c3689cb1f171ab45c907ddde454a
“If Amazon SQS has already accepted a message with a specific deduplication ID, any subsequent messages with the same ID will be acknowledged but not delivered to consumers.”
S4 · amazon.com · Using the message deduplication ID in Amazon SQS · version ebcc5fd648fd4a60b2f982a6ed31159a3fb7c3689cb1f171ab45c907ddde454a
How does SQS FIFO ordering work according to current official AWS sources?
1 recorded excerpt remain.
Inspect remaining excerpts
“FIFO queues add producer-side deduplication and strict ordering within each message group.”
S1 · oneuptime.com · SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee · version e4200a54840f3c862fa849e1b48e2724d9195024025f56e0659566501adc7d0e
How does SQS FIFO redelivery work according to current official AWS sources?
1 recorded excerpt remain.
Inspect remaining excerpts
“Consumer redelivery: one queued message is received again after failed or incomplete settlement.”
S1 · oneuptime.com · SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee · version e4200a54840f3c862fa849e1b48e2724d9195024025f56e0659566501adc7d0e
How does application idempotency relate to SQS FIFO queues according to current official AWS sources?
2 recorded excerpts remain.
Inspect remaining excerpts
“Use FIFO to control queue-introduced duplicates and per-group order; use application idempotency to control repeated effects.”
S1 · oneuptime.com · SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee · version e4200a54840f3c862fa849e1b48e2724d9195024025f56e0659566501adc7d0e
“Long-lived API idempotency requires a durable application record, not just FIFO's recent-send memory.”
S1 · oneuptime.com · SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee · version e4200a54840f3c862fa849e1b48e2724d9195024025f56e0659566501adc7d0e
What is the short adoption decision for changing an SQS standard queue to FIFO to address duplicate external side effects when a worker crashes after a successful API call but before deleting the message?
2 recorded excerpts remain.
Inspect remaining excerpts
“Use FIFO to control queue-introduced duplicates and per-group order; use application idempotency to control repeated effects.”
S1 · oneuptime.com · SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee · version e4200a54840f3c862fa849e1b48e2724d9195024025f56e0659566501adc7d0e
“Keep the latter order and make the effect idempotent.”
S1 · oneuptime.com · SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee · version e4200a54840f3c862fa849e1b48e2724d9195024025f56e0659566501adc7d0e
Targets are requested topics, not verified assertions. Excerpts do not prove truth or independent corroboration. This view keeps the answer, confidence and payments unchanged and makes no new requests.
Research evidence matrix
Compare unverified research targets with cited sources and inspect recorded excerpts. An empty cell means no inspectable excerpt was recorded; it does not establish whether a claim is true, false, or disputed. Coverage and agent confidence do not prove entailment, measured accuracy or complete synthesis.
| Research target (unverified) | Inspection status | [S1] SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not GuaranteePublication: oneuptime.comPublished: Not recorded | [S4] Using the message deduplication ID in Amazon SQSPublication: amazon.comPublished: Not recorded |
|---|---|---|---|
| Does changing an SQS standard queue to FIFO eliminate duplicate external side effects when a worker crashes after a successful API call but before deleting the message? | Recorded excerpt | Inspect 2 excerptsA FIFO consumer can still execute business code again after its visibility timeout expires or after it commits an effect and fails before deleting the message. AWS calls the FIFO feature “exactly-once processing,” but its documented mechanism does not make your database update and DeleteMessage one atomic operation. | No excerpt recorded |
| What is the documented deduplication window for SQS FIFO queues according to current official AWS sources? | Recorded excerpt | No excerpt recorded | Inspect 1 excerptIt ensures that within a 5-minute deduplication window, only one instance of a message with the same deduplication ID is processed and delivered. |
| What are the explicit limits of any exactly-once claim for SQS FIFO queues according to current official AWS sources? | Recorded excerpt | Inspect 2 excerptsAWS calls the FIFO feature “exactly-once processing,” but its documented mechanism does not make your database update and DeleteMessage one atomic operation. There is no distributed transaction joining an arbitrary database or external API to SQS deletion. | No excerpt recorded |
| How does SQS FIFO send deduplication work according to current official AWS sources? | Recorded excerpt | No excerpt recorded | Inspect 2 excerptsMessageDeduplicationId is a token used only in Amazon SQS FIFO queues to prevent duplicate message delivery. If Amazon SQS has already accepted a message with a specific deduplication ID, any subsequent messages with the same ID will be acknowledged but not delivered to consumers. |
| How does SQS FIFO ordering work according to current official AWS sources? | Recorded excerpt | Inspect 1 excerptFIFO queues add producer-side deduplication and strict ordering within each message group. | No excerpt recorded |
| How does SQS FIFO redelivery work according to current official AWS sources? | Recorded excerpt | Inspect 1 excerptConsumer redelivery: one queued message is received again after failed or incomplete settlement. | No excerpt recorded |
| How does application idempotency relate to SQS FIFO queues according to current official AWS sources? | Recorded excerpt | Inspect 2 excerptsUse FIFO to control queue-introduced duplicates and per-group order; use application idempotency to control repeated effects. Long-lived API idempotency requires a durable application record, not just FIFO's recent-send memory. | No excerpt recorded |
| What is the short adoption decision for changing an SQS standard queue to FIFO to address duplicate external side effects when a worker crashes after a successful API call but before deleting the message? | Recorded excerpt | Inspect 2 excerptsUse FIFO to control queue-introduced duplicates and per-group order; use application idempotency to control repeated effects. Keep the latter order and make the effect idempotent. | No excerpt recorded |
Reference export
2 article references. Recorded titles, links and dates; observed scholarly records also include supplied authors, DOI and journal metadata with read limits. Review metadata before using in a paper. Import RIS into Zotero with File → Import.
Cited sources and references
- 1SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guaranteeoneuptime.comFree public reference · no creator payment · extracted html text65%
- 4Using the message deduplication ID in Amazon SQSamazon.comFree public reference · no creator payment · extracted html text35%
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Decision log · 69 steps
Breaking down: "Would changing an SQS standard queue to FIFO eliminate duplicate external side effects when a worker crashes after a successful API call but before deleting the message? Find current official AWS sources. Produce a short adoption decision and compare send deduplication, ordering, redelivery and application idempotency. Include the documented deduplication window and explicit limits of any exactly-once claim."
Identified 8 research target(s) to investigate; these are not established facts
Deep mode: up to 4 paid/cached/public reads plus one bounded gap-expansion pass when needed.
Web search: 4/4 planned queries attempted, 3 succeeded, 19 public page previews, 1 unavailable queries. Snippets are discovery only. Public reads spend no USDC; model and service operating costs remain separate.
Discovered 0 verified creator source(s) and 19 free public reference(s)
Claim-aware portfolio (exhaustive; bounded selection, not a claim of global optimality) selected 4/8 positive proposal(s): 4 free/cache selections + 0 paid fresh selections, predicting 7/8 claim(s) above the evidence floor with $0.000000/$0.015000 fetch USDC reserved.
Free-preview pre-check covers 7/8 sub-claims (88%). The agent may buy only claim-targeted sources and will label the answer provisional if paid evidence stays thin.
Preview directly addresses the core scenario: worker commits an external effect then crashes before DeleteMessage, and states FIFO does not introduce a second queued send but the consumer can still re-execute business code — exactly the distinction between queue-introduced duplicates and application idempotency. Covers the central question and the exactly-once limits. - free public original-page READ selection (not a cache hit); no purchase or creator reward. — selected for the claim-aware evidence portfolio (targets claims 1, 3, 7, 8; 0 fetch USDC, 1 attention slot).
Official AWS SQS queue types documentation preview states FIFO exactly-once processing and MessageDeduplicationId behavior — the authoritative source for the exactly-once claim, deduplication, and adoption decision. - free public original-page READ selection (not a cache hit); no purchase or creator reward. — selected for the claim-aware evidence portfolio (targets claims 2, 3, 4, 8; 0 fetch USDC, 1 attention slot).
Preview explicitly enumerates the two conditions for FIFO exactly-once (publishers not duplicating beyond five minutes, consumers always deleting after processing) and the need to store a durable copy before deleting — directly relevant to the limits of exactly-once and the crash-before-delete scenario. - free public original-page READ selection (not a cache hit); no purchase or creator reward. — selected for the claim-aware evidence portfolio (targets claims 1, 3, 6, 7; 0 fetch USDC, 1 attention slot).
Official AWS documentation page on MessageDeduplicationId explicitly states the 5-minute deduplication window and that only one instance with the same ID is processed and delivered — the authoritative source for the deduplication window and send-deduplication subclaims. - free public original-page READ selection (not a cache hit); no purchase or creator reward. — selected for the claim-aware evidence portfolio (targets claims 2, 4; 0 fetch USDC, 1 attention slot).
Generic Standard-vs-FIFO overview with a symptom table; preview mentions reprocessing when handler throws before delete but adds little beyond the stronger candidates and is not an official AWS source. - free public original-page READ selection (not a cache hit); no purchase or creator reward.
Preview explains MessageDeduplicationId and the 5-minute window during which duplicate sends are accepted but not delivered, supporting the send-deduplication and deduplication-window subclaims. - free public original-page READ selection (not a cache hit); no purchase or creator reward. — the claim-aware portfolio chose a stronger, less redundant set inside the 4-source attention and $0.015000 fetch-budget caps, so this proposal stays unspent.
YouTube overview of FIFO deduplication and ordering; transcript preview is thin and non-official, adding little over the AWS docs and detailed blog posts already selected. - free public original-page READ selection (not a cache hit); no purchase or creator reward.
Preview describes redelivery after visibility timeout when a message is not deleted, which is the mechanism behind the duplicate-side-effect scenario and supports the redelivery subclaim. - free public original-page READ selection (not a cache hit); no purchase or creator reward. — the claim-aware portfolio chose a stronger, less redundant set inside the 4-source attention and $0.015000 fetch-budget caps, so this proposal stays unspent.
Reddit thread snippet only asserts at-least-once delivery and handler idempotency in passing; no substantive detail on FIFO deduplication window, ordering, or exactly-once limits. - free public original-page READ selection (not a cache hit); no purchase or creator reward.
About SQS 500 Internal Failure errors on FIFO high-throughput queues; unrelated to deduplication, ordering, redelivery, or idempotency. - free public original-page READ selection (not a cache hit); no purchase or creator reward.
Stack Overflow question about FIFO queues returning empty on poll; not relevant to duplicate side effects, deduplication window, or exactly-once limits. - free public original-page READ selection (not a cache hit); no purchase or creator reward.
Preview states FIFO queues deduplicate within a 5-minute window using MessageDeduplicationId and that only the first message is accepted — directly supports the deduplication window and send-deduplication subclaims. - free public original-page READ selection (not a cache hit); no purchase or creator reward. — the claim-aware portfolio chose a stronger, less redundant set inside the 4-source attention and $0.015000 fetch-budget caps, so this proposal stays unspent.
Preview details MessageDeduplicationId and the 5-minute window plus content-based deduplication guidance, supporting the deduplication window and send-deduplication subclaims. - free public original-page READ selection (not a cache hit); no purchase or creator reward. — the claim-aware portfolio chose a stronger, less redundant set inside the 4-source attention and $0.015000 fetch-budget caps, so this proposal stays unspent.
re:Post thread confirms the 5-minute deduplication window but the preview is a partial user exchange and adds no authoritative detail beyond the AWS docs and blog sources already selected. - free public original-page READ selection (not a cache hit); no purchase or creator reward.
YouTube video description on FIFO deduplication; preview is only metadata and a brief description, redundant with the written deduplication sources. - free public original-page READ selection (not a cache hit); no purchase or creator reward.
Reddit snippet only mentions content hashing for FIFO deduplication in passing; no detail on window, ordering, redelivery, or exactly-once limits. - free public original-page READ selection (not a cache hit); no purchase or creator reward.
Stack Overflow question about changing the deduplication interval; preview only references the developer guide and does not itself provide authoritative content. - free public original-page READ selection (not a cache hit); no purchase or creator reward.
GitHub discussion about in-flight message limits for FIFO queues; tangential to duplicate side effects, deduplication window, and exactly-once limits. - free public original-page READ selection (not a cache hit); no purchase or creator reward.
Vendor blog restating FIFO ordering and exactly-once claims; non-official and redundant with the AWS documentation and detailed blog analyses already selected. - free public original-page READ selection (not a cache hit); no purchase or creator reward.
READ SQS Standard vs. FIFO: What Exactly-Once Processing Does and Does Not Guarantee - selected original public page, 0 USDC; not a cache hit.
Read extracted public text from https://oneuptime.com/blog/post/2026-07-22-sqs-standard-vs-fifo-exactly-once/view - S1; quote matching establishes source grounding, not fact verification.
READ Amazon SQS queue types - Amazon Simple Queue Service - selected original public page, 0 USDC; not a cache hit.
Read extracted public text from https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-queue-types.html - S2; quote matching establishes source grounding, not fact verification.
READ Dissecting SQS FIFO Queues — Does Ordered and Exactly Once Messaging Really Exist? | Kevin Sookocheff - selected original public page, 0 USDC; not a cache hit.
Read extracted public text from https://sookocheff.com/post/messaging/dissecting-sqs-fifo-queues/ - S3; quote matching establishes source grounding, not fact verification.
READ Using the message deduplication ID in Amazon SQS - Amazon Simple Queue Service - selected original public page, 0 USDC; not a cache hit.
Read extracted public text from https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/using-messagededuplicationid-property.html - S4; quote matching establishes source grounding, not fact verification.
Attention budget is full at 4 source(s); no broader context will be purchased.
Final check — "Does changing an SQS standard queue to FIFO eliminate duplic…": 90% assessed by S1, S2
Final check — "What is the documented deduplication window for SQS FIFO que…": 100% assessed by S4, S3
Final check — "What are the explicit limits of any exactly-once claim for S…": 60% assessed by S2, S1
Final check — "How does SQS FIFO send deduplication work according to curre…": 100% assessed by S4, S2
Final check — "How does SQS FIFO ordering work according to current officia…": 80% assessed by S1, S3, S2
Final check — "How does SQS FIFO redelivery work according to current offic…": 60% assessed by S1, S3
Final check — "How does application idempotency relate to SQS FIFO queues a…": 60% assessed by S1, S2
Final check — "What is the short adoption decision for changing an SQS stan…": 90% assessed by S1, S2, S4
Final coverage assessment — The supplied sources directly answer the core question: FIFO does not eliminate duplicate external side effects when a worker crashes after a successful API call but before deleting the message, because SQS deletion is not atomic with the external effect; application idempotency is still required. They also document the 5-minute deduplication window, send deduplication behavior, ordering, redelivery, and the limits of the exactly-once claim. The adoption decision is supported: FIFO can reduce queue-introduced duplicates and preserve per-group order, but it is not sufficient for external side-effect exactly-once; keep delete-after-effect and make the effect idempotent. Some requested details, such as a fully official AWS statement on redelivery mechanics and a more explicit official AWS limits-of-exactly-once statement, are only partially covered by the supplied passages. The assessment does not establish a complete supported answer for every requested part.
Synthesizing a grounded answer from 4 source(s)…
Relevance review returned; only checked excerpts can retain support, and review cannot raise it.
⚖️ Sources disagreed on Whether FIFO's exactly-once processing prevents duplicate external side effects — S2 States 'Exactly-once processing – FIFO queues deliver each message once and keep it available until you process and delete it,' implying each message is processed once. vs S1 States AWS calls the FIFO feature 'exactly-once processing,' but its documented mechanism does not make the database update and DeleteMessage atomic, and a FIFO consumer can still execute business code again after a visibility-timeout expiry or after committing an effect and failing before deleting the message. → reported preference: S1 (S1 is more specific and internally consistent: it explains the exact failure mode (no atomicity between the external effect and DeleteMessage) and the bounded nature of the deduplication window, whereas S2's one-line definition is a high-level paraphrase that does not address the crash-between-effect-and-delete scenario.)
Delivering qualified source excerpts; complete synthesis and per-assertion support remain unverified.
Source-matched public excerpt (no creator reward) — S1, research target 1, proposed support 90% (estimate, not entailment): “A FIFO consumer can still execute business code again after its visibility timeout expires or after it commits an effect and fails before de…”
Source-matched public excerpt (no creator reward) — S1, research target 1, proposed support 80% (estimate, not entailment): “AWS calls the FIFO feature “exactly-once processing,” but its documented mechanism does not make your database update and DeleteMessage one …”
Source-matched public excerpt (no creator reward) — S4, research target 2, proposed support 90% (estimate, not entailment): “It ensures that within a 5-minute deduplication window, only one instance of a message with the same deduplication ID is processed and deliv…”
Below support/reward gate — S4, research target 2, proposed support 20% (estimate, not entailment): “Amazon SQS continues tracking the deduplication ID even after the message has been received and deleted.”
Source-matched public excerpt (no creator reward) — S1, research target 3, proposed support 80% (estimate, not entailment): “AWS calls the FIFO feature “exactly-once processing,” but its documented mechanism does not make your database update and DeleteMessage one …”
Source-matched public excerpt (no creator reward) — S1, research target 3, proposed support 85% (estimate, not entailment): “There is no distributed transaction joining an arbitrary database or external API to SQS deletion.”
Source-matched public excerpt (no creator reward) — S4, research target 4, proposed support 50% (estimate, not entailment): “MessageDeduplicationId is a token used only in Amazon SQS FIFO queues to prevent duplicate message delivery.”
Source-matched public excerpt (no creator reward) — S4, research target 4, proposed support 80% (estimate, not entailment): “If Amazon SQS has already accepted a message with a specific deduplication ID, any subsequent messages with the same ID will be acknowledged…”
Source-matched public excerpt (no creator reward) — S1, research target 5, proposed support 60% (estimate, not entailment): “FIFO queues add producer-side deduplication and strict ordering within each message group.”
Source-matched public excerpt (no creator reward) — S1, research target 6, proposed support 70% (estimate, not entailment): “Consumer redelivery: one queued message is received again after failed or incomplete settlement.”
Below support/reward gate — S1, research target 6, proposed support 10% (estimate, not entailment): “The handler must be idempotent.”
Source-matched public excerpt (no creator reward) — S1, research target 7, proposed support 80% (estimate, not entailment): “Use FIFO to control queue-introduced duplicates and per-group order; use application idempotency to control repeated effects.”
Source-matched public excerpt (no creator reward) — S1, research target 7, proposed support 80% (estimate, not entailment): “Long-lived API idempotency requires a durable application record, not just FIFO's recent-send memory.”
Source-matched public excerpt (no creator reward) — S1, research target 8, proposed support 70% (estimate, not entailment): “Use FIFO to control queue-introduced duplicates and per-group order; use application idempotency to control repeated effects.”
Source-matched public excerpt (no creator reward) — S1, research target 8, proposed support 40% (estimate, not entailment): “Keep the latter order and make the effect idempotent.”
Rejected 0 invalid evidence span(s) and 1 unsupported citation marker(s); rejected markers cannot receive citation rewards.
Prepared source excerpts citing 2 source(s); complete synthesis is unverified
Confidence: Low — Only source excerpts are delivered; complete synthesis and per-assertion support remain unverified. Evidence assessment: the final assessment does not establish a complete supported answer for every requested part.
oneuptime.com contributed 65% - free public reference; reward share withheld
amazon.com contributed 35% - free public reference; reward share withheld
Done. Spent $0 across 0 confirmed/simulated payment(s) to creators.
Portable research receipt
Take the evidence trail with you
One deterministic JSON bundle binds the answer, visible decisions, exact article versions, claim evidence and a Circle-settlement snapshot under SHA-256. Retain the digest to detect later changes; the self-check is not a publisher or Keryx signature.
Carries this dispatch’s question as context — never its answer. The next dispatch is read from sources bought for it.