HKT windows and handoff markers
Flow KPIs can move when clocks and handoff tags move—not when the product does.
Teams serving users in Hong Kong often mix UTC warehouse timestamps with HKT operations calendars. A cohort day that spans the wrong midnight shifts every dwell and throughput cell without anyone shipping a feature.
Missing or duplicated handoff markers create similar ghosts: returning users appear as new cohorts, and day-seven rates look healthier or worse depending on merge rules.
Before celebrating a flow lift after a platform migration, list SDK versions, identity rules, timezone settings, and handoff tags beside the chart. If those moved, treat the chart as suspect until you rebuild from raw events.