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Two Sources of Truth Will Always Disagree

Somewhere in your system the same fact is stored twice. A count in a column and the rows it is counting. A status on the order and a status on the payment.

  • Two sources of data for the same fact will inevitably diverge over time
  • Discrepancies can result from write failures, off-peak jobs, or partial migrations
  • Systems must identify the accurate source, as both are considered truth

The shell step that could not fail no matter what we did to it

Our integration suite had been green for eleven weeks. That is not a boast, it is the symptom. A colleague onboarding to the repo wrote a deliberately broken test to see what a failure looked like…

  • Shell step npm run test:integration | tee integration.log || true contained two errors
  • set -o pipefail absent, causing pipeline exit status to always be zero
  • Fix: all scripts began with set -euo pipefail

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