Skip to content
Advanced SRELesson 4 of 5 2 min read

Postmortems & Blameless Culture

Turning an outage into the thing that prevents the next three.

Skip to the challenge
On this page4 sections

Once an incident is over and the mitigation has held, the most valuable part of the whole process starts: writing it up so it's genuinely less likely to happen again.

Anatomy of a postmortem

A good postmortem is a short, specific document, not a novel:

  • Timeline - what happened, in order, with real timestamps.
  • Impact - who was affected, for how long, and how badly.
  • Root cause - what actually, specifically caused it - not just "the server crashed," but why it crashed.
  • Action items - concrete follow-up work, each with a named owner and a deadline.

That last point matters more than it looks: a postmortem with no owned, deadlined action items is just a very detailed way of describing a problem that will happen again.

Blameless, on purpose

A blameless postmortem asks "what about our systems and processes allowed this to happen?" - never "who caused this?" This isn't a nicety; it's load-bearing for the whole process. If writing an honest timeline risks someone getting blamed, people learn - quickly, and rationally - to leave out inconvenient details or avoid flagging problems early. A team only gets the full, honest story when being part of an incident doesn't feel like a personal risk to admit to.

It's a learning artifact, not paperwork

The best postmortems get read by people who weren't even involved in the incident - they're how an organization's hard-won lessons about its own system spread beyond the handful of people who happened to be on call that night.

Try it

Run these in the practice terminal (opens in a new tab). It opens in a new tab, so you keep your place here.
bash
touch postmortem.md

When you're ready, hit Mark complete and move to the next lesson.

Challenge

Create the file where this incident's postmortem will be written up.

Want to experiment first? Try things in the practice terminal (opens in a new tab), then enter the command that solves the task here.

Quiz

Lock in the concepts. Score at least 80% to mark the lesson complete.

0 of 2 answered

Done with this one?

Skipped the challenge? You can mark the lesson complete by hand.

Your notes

Kept on this browser only.