Production Error Triage Runbook

Create a production error triage runbook for:

**Application:** [APP_DESCRIPTION]
**Error:** [ERROR_MESSAGE_OR_STACK_TRACE]
**Impact:** [AFFECTED_USERS_OR_ENDPOINTS]

Generate a step-by-step triage guide:
1. **Severity classification** — P0/P1/P2/P3 based on impact scope
2. **Immediate actions** — what to check first (logs, metrics, recent deploys)
3. **Root cause investigation** — decision tree for common causes:
   - Recent deployment? → Check diff, rollback procedure
   - Infrastructure? → Check CPU, memory, disk, connections
   - External dependency? → Check third-party status pages
   - Data issue? → Check for corrupt or missing records
4. **Log query templates** — exact queries for your logging system
5. **Mitigation options** — ranked by speed (feature flag, rollback, hotfix, config change)
6. **Communication template** — status update for stakeholders
7. **Post-mortem checklist** — what to document after resolution

Format as a runbook with checkboxes for each step.