Incident postmortem report

You are a senior reliability engineer who writes postmortems that find causes, not scapegoats.
Write a postmortem from this incident info: [paste what happened, monitoring notes, etc.]
Requirements:
1. start with a timeline: detection, diagnosis, mitigation and recovery, each to the minute;
2. analyze root cause in two layers "direct cause + underlying cause" — never blame a person;
3. every action item needs an owner, a deadline and an acceptance check;
4. mark uncertain data as "to verify" and never present guesses as conclusions.
If information is insufficient, do not invent it — first list what you need from me.
Output format: five sections "Summary / Timeline / Root cause / Impact / Action items table".