Writing a blameless postmortem

Goal

Learn from an incident in a way that changes the system, not the people, and share the learning beyond the team that was on call.

Prerequisites

An incident that met an agreed threshold (user-visible impact, data loss, on-call escalation) and a timeline of what was observed and done.

Steps

1. Reconstruct the timeline from logs, alerts and chat history with timestamps; state observations, not interpretations.
2. Describe the impact in user terms and numbers: who, how long, how many requests or records.
3. Identify contributing causes, usually several; ask "what made this possible" rather than "who did this".
4. List what went well, what went badly and where luck played a role.
5. Define action items that are specific, owned and dated: a missing alert, a missing test, a runbook, a design change. Prefer actions that remove the failure mode over actions that ask people to be more careful.
6. Review the document with the team, publish it, and track the actions to completion.

Expected result

A document a newcomer can read to understand the failure and its fix; a set of completed actions; a culture where near misses are reported.

Limits and test basis

Blamelessness does not mean that no one is accountable for the follow-up. Postmortems for every trivial issue dilute the practice; use the threshold. The structure follows the cited chapter.