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Critical Flow — A Price Change Becomes Searchable

Fifteen messages, and the acknowledgement that deliberately arrives before the document is searchable.

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Inventory Source Capture Tier Change Log Assembly Assembly State Fast Lane Writer idx_v41 Query Service 1. price changed, v812 2. schema check 3. applied version? 4. v811 5. append (key, v812) 6. committed 7. ack 8. fast-lane consume 9. guard + record v812 10. partial update 11. bulk upsert 12. refreshed 13. search via alias 14. hits + index version 15. attach freshness Critical Flow — A Price Change Becomes Searchable Message 7 is the acknowledgement: the source is free once the change is durable, not once it is searchable. v 1.0 · owner Data Platform Architecture

Decisions

  • Message 7 is the source's acknowledgement, sent once the change is durable in the log — not once it is indexed. That single ordering is what keeps the accept path fast and the lanes independent.
  • The version guard runs twice: at capture against assembly state, and again at apply, so a reordered redelivery cannot regress a document in either place.
  • The fast lane performs a partial update: no join, no enrichment, no document reassembly for a field that changes hundreds of times an hour on a popular item.
  • The query response is stamped with the index version and observed freshness at message 15, so the caller can judge the answer rather than trust it.

Assumptions

  • Ingestion accept p99 ≤ 50 ms single change; fast lane source-commit-to-searchable p95 ≤ 2 s, p99 ≤ 10 s.

Risks

  • A cluster refresh interval that is tuned for indexing throughput will quietly spend the fast lane's entire budget.
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Solution Architecture v1.0 · Amazon Web Services · Data Platform Architecture · 2026-1013-critical-flow-change-to-searchable