What they're testing
Whether you have engineering culture — this is a question about a team, not about tooling.
The short answer~30 seconds
A timeline with real clock times (when it was detected, who was paged, when it recovered), measured impact (how many users, for how long, what it cost in money or error budget), causes in layers rather than one line, and actions with an OWNER and a DEADLINE. Most importantly: no person named as the cause. If one hand-typed command took production down, the real finding is the system that allowed it to.
The long answer
Blamelessness isn't politeness but effectiveness: where people are reprimanded, people stop reporting. You lose the near-misses — the cheapest and most valuable information available — because nobody wants to record that they almost broke something. The more psychologically safe the team, the more it knows about its own system.
The weakest section of most postmortems is the action list: "be more careful" or "add documentation" aren't actions, because neither is measurable nor checkable. A good action changes the SYSTEM: an alert with a specific threshold, a confirmation before a dangerous command, a CI check blocking the misconfiguration. If the action doesn't change the system's behaviour, the incident will recur.
On measurement, two numbers are worth tracking over time more than incident count: time to DETECT and time to RECOVER. Incident count depends on change velocity and isn't inherently bad; slow detection always is, and it usually points at a gap in observability rather than in code.
What they'll ask next
?Do small incidents need a postmortem?
A short one, because small incidents are usually a preview of a large one with the same cause. Set an explicit trigger (any error-budget breach, say, or any out-of-hours page) so it isn't debated case by case.
These lose points
- A root cause of "human error". Humans are part of the system; the next question has to be why the system let that error have that consequence.
- Actions with no owner and no deadline. They won't happen, and the next postmortem will list them again.