http://foojayio.github.io/website/today/author/yuelin-ou/Articles written by Yuelin Ou on foojay.io - Friends Of OpenJDKHugoen-usMon, 17 Aug 2026 06:46:00 +0000http://foojayio.github.io/website/today/idempotent-write-paths-keeping-an-integration-pipeline-correct-when-messages-repeat/Mon, 17 Aug 2026 06:46:00 +0000http://foojayio.github.io/website/today/idempotent-write-paths-keeping-an-integration-pipeline-correct-when-messages-repeat/<h2 id="a-reconciliation-that-didnt-add-up">A reconciliation that didn&rsquo;t add up</h2> <p>Let me start with a real one. After a big sales promo, during reconciliation, finance said a batch of orders had the wrong status: on our side it showed &ldquo;paid&rdquo;, but the finance system hadn&rsquo;t booked it.</p> <p>Tracing it back, we found the payment gateway had retried during its peak, and the same payment notification got pushed twice. The first one was processed normally; the second time it came, the consumer happened to be in the middle of a rolling restart, so the message got re-queued and consumed again.</p>