When HKT midnight rewrites your p95
Day-one performance cohorts can shift when midnight moves—not when the network does.
Application teams serving Hong Kong often mix UTC event stores with HKT product calendars. A cohort day that spans the wrong midnight rewrites every performance cell without a single topology change.
Agent upgrades that change sample stitching create similar ghosts. Returning sessions look new; p95 numbers swing for pipeline reasons.
Before celebrating a lift, list agent versions, correlation rules, and timezone settings beside the chart. Our Monitoring Signal Review always opens with that checklist.