Write a runbook someone reads at 3am

Write a runbook for this scenario.

Structure, strictly in this order:
1. **Is this the right runbook?** Two or three symptoms that confirm it. If they do not match, where to go instead.
2. **Stop the bleeding.** The single fastest mitigation, as a command or a click path. *This is the first thing on the page.*
3. **Steps.** Numbered. One action each. Command or exact UI path, then what a correct result looks like, then what to do if it does not.
4. **Danger markers** — steps that are irreversible, destroy data, or affect other systems. Mark each inline, before the step, not after.
5. **Escalation** — who to wake, at what point, and what to tell them.
6. **Verification** — how to confirm it is actually fixed, not just quiet.
7. **Background** — why this happens. *Last. Nobody reads this during an incident.*

Rules:
- Write for someone tired, under pressure, who did not build this system.
- *Commands must be copy-pasteable.* No placeholders like `<your-region>` without saying where to find the value.
- Every step states its expected result. A step you cannot verify is a step that silently fails.
- Where the procedure I gave you has a gap, say "unknown — find out before this is needed" rather than filling it in.