The judgment calls behind the work, and where we’ve written them up.

We match the old numbers before we improve them. A migration’s first job is parity with the legacy system, even where the legacy logic is arguably wrong. Quietly “fixing” numbers nobody asked to change starts a new argument with finance. How we ran Phase 2

We test against what runs, not what’s written down. Documentation drifts. On one engagement, logic built strictly to the documentation produced a count more than 70% too high. Testing against the production system caught it before cutover. The full story

We measure before we promise. “Near real-time” is a claim until it’s a number. On our reference build: 2–4 minutes under controlled load, 2–8 minutes in production, with the one setting that moves it identified. The measurements

Reconciliation is a control, not a project phase. Independent checks compare the hub with its sources on every load, for as long as it runs. The case study