Dual-run weeks that do not quietly drift forever
Dual-run sounds safe: keep the old path alive while the new path proves itself. Without an exit date and exit checks, dual-run becomes a second production you never intended to fund. Latency comparisons go stale, ownership blurs, and nobody wants to be the person who switches the old path off.
When we design sequencing, we write the dual-run start and the dual-run exit in the same paragraph. Exit checks might include error budgets, reconciliation counts, or a named number of clean business days. If those checks cannot be stated, the dual-run is not ready to begin.
Drift happens quietly. A calendar reminder is not enough — put the exit on the cutover runbook with an owner who can call it even when feature pressure asks for “one more week.”