By name: incident-postmortem description: Write a blameless, actionable incident postmortem from the raw facts. Use after an outage/incident, or when asked to write up "what happened" for the team. version: 1.0.0 license: MIT keywords: [postmortem, incident, outage, sre, writing]
incident-postmortem
A postmortem exists to change the system, not to assign blame or to perform remorse. Optimize for the engineer two years from now who hits something similar at 3am.
Procedure
- Timeline first, from artifacts. Build it from logs, alerts, deploy records and chat timestamps — not memory. Every entry: time (with zone), what happened, what was known at that moment. Mark detection, diagnosis, mitigation, resolution.
- Impact, quantified. Who/what/how long/how many: "checkout failed for 12 customers over 3h; all recovered" beats "some users were affected".
- Root cause as a causal chain, not a single line. Use "because" links: webhooks dropped → because the endpoint 500'd on duplicates → because a unique-constraint violation was treated as fatal → because the handler assumed Stripe never retries. The last "because" is usually an assumption, and assumptions are what you fix.
- Blameless mechanically: name systems and decisions, not people. "The deploy script allowed a config-less rollout" — not "X forgot the config". If a person had to be careful for the system to be safe, that's the finding.
- What went well / what got lucky. Luck is a finding too ("we noticed only because someone happened to be watching dashboards").
- Action items that would have prevented or shortened THIS incident, each with an owner and a date. Test each one: "would this have helped on the timeline above?" If not, cut it. 3–5 strong items beat 15 aspirational ones.
Skeleton
# 2026-04-02 — Payments webhook outage (3h, 12 failed checkouts)
**Summary** (3 sentences: what broke, impact, fix)
**Timeline** (timestamped, detection → resolution)
**Root cause** (causal chain, ending at the broken assumption)
**What went well / what got lucky**
**Action items** (owner · due date · "would it have helped?")