Readiness
What separates a runbook that helps at 3am from one that does not?
Whether the candidate writes procedures for a tired stranger with partial information, and knows what a runbook must not contain.
The situation behind the question
The on-call runbook for a payments service has three steps: "1. Check the dashboard. 2. If it looks bad, restart the pods. 3. If that does not work, escalate." It has resolved incidents twice and destroyed the evidence in four others.