| name | home-postmortem-writing |
| description | Write effective blameless postmortems with root cause analysis, timelines, and action items. Use when conducting incident reviews, writing postmortem documents, or improving incident response processes. |
Postmortem Writing
Comprehensive guide to writing effective, blameless postmortems that drive organizational learning and prevent incident recurrence.
When to Use This Skill
- Conducting post-incident reviews
- Writing postmortem documents
- Facilitating blameless postmortem meetings
- Identifying root causes and contributing factors
- Creating actionable follow-up items
- Building organizational learning culture
Core Concepts
1. Blameless Culture
| Blame-Focused | Blameless |
|---|
| "Who caused this?" | "What conditions allowed this?" |
| "Someone made a mistake" | "The system allowed this mistake" |
| Punish individuals | Improve systems |
| Hide information | Share learnings |
| Fear of speaking up | Psychological safety |
2. Postmortem Triggers
- SEV1 or SEV2 incidents
- Customer-facing outages > 15 minutes
- Data loss or security incidents
- Near-misses that could have been severe
- Novel failure modes
- Incidents requiring unusual intervention
Quick Start
Postmortem Timeline
Day 0: Incident occurs
Day 1-2: Draft postmortem document
Day 3-5: Postmortem meeting
Day 5-7: Finalize document, create tickets
Week 2+: Action item completion
Quarterly: Review patterns across incidents
Templates and detailed worked examples
Full template library and detailed worked examples live in references/details.md. Read that file when you need the concrete templates.
References
### Template 2: 5 Whys Analysis
```markdown
# 5 Whys Analysis: [Incident]
## Problem Statement
Payment service experienced 47-minute outage due to database connection exhaustion.
## Analysis
### Why #1: Why did the service fail?
**Answer**: Database connections were exhausted, causing all new requests to fail.
**Evidence**: Metrics showed connection count at 100/100 (max), with 500+ pending requests.
---
### Why #2: Why were database connections exhausted?
**Answer**: Each incoming request opened a new database connection instead of using the connection pool.
**Evidence**: Code diff shows direct `DriverManager.getConnection()` instead of pooled `DataSource`.
---
### Why #3: Why did the code bypass the connection pool?
**Answer**: A developer refactored the repository class and inadvertently changed the connection acquisition method.
**Evidence**: PR #1234 shows the change, made while fixing a different bug.
---
### Why #4: Why wasn't this caught in code review?
**Answer**: The reviewer focused on the functional change (the bug fix) and didn't notice the infrastructure change.
**Evidence**: Review comments only discuss business logic.
---
### Why #5: Why isn't there a safety net for this type of change?
**Answer**: We lack automated tests that verify connection pool behavior and lack documentation about our connection patterns.
**Evidence**: Test suite has no tests for connection handling; wiki has no article on database connections.
## Root Causes Identified
1. **Primary**: Missing automated tests for infrastructure behavior
2. **Secondary**: Insufficient documentation of architectural patterns
3. **Tertiary**: Code review checklist doesn't include infrastructure considerations
## Systemic Improvements
| Root Cause | Improvement | Type |
| ------------- | --------------------------------- | ---------- |
| Missing tests | Add infrastructure behavior tests | Prevention |
| Missing docs | Document connection patterns | Prevention |
| Review gaps | Update review checklist | Detection |
| No canary | Implement canary deployments | Mitigation |
Template 3: Quick Postmortem (Minor Incidents)
# Quick Postmortem: [Brief Title]
**Date**: 2024-01-15 | **Duration**: 12 min | **Severity**: SEV3
## What Happened
API latency spiked to 5s due to cache miss storm after cache flush.
## Timeline
- 10:00 - Cache flush initiated for config update
- 10:02 - Latency alerts fire
- 10:05 - Identified as cache miss storm
- 10:08 - Enabled cache warming
- 10:12 - Latency normalized
## Root Cause
Full cache flush for minor config update caused thundering herd.
## Fix
- Immediate: Enabled cache warming
- Long-term: Implement partial cache invalidation (ENG-999)
## Lessons
Don't full-flush cache in production; use targeted invalidation.
Facilitation Guide
Running a Postmortem Meeting
## Meeting Structure (60 minutes)
### 1. Opening (5 min)
- Remind everyone of blameless culture
- "We're here to learn, not to blame"
- Review meeting norms
### 2. Timeline Review (15 min)
- Walk through events chronologically
- Ask clarifying questions
- Identify gaps in timeline
### 3. Analysis Discussion (20 min)
- What failed?
- Why did it fail?
- What conditions allowed this?
- What would have prevented it?
### 4. Action Items (15 min)
- Brainstorm improvements
- Prioritize by impact and effort
- Assign owners and due dates
### 5. Closing (5 min)
- Summarize key learnings
- Confirm action item owners
- Schedule follow-up if needed
## Facilitation Tips
- Keep discussion on track
- Redirect blame to systems
- Encourage quiet participants
- Document dissenting views
- Time-box tangents
Anti-Patterns to Avoid
| Anti-Pattern | Problem | Better Approach |
|---|
| Blame game | Shuts down learning | Focus on systems |
| Shallow analysis | Doesn't prevent recurrence | Ask "why" 5 times |
| No action items | Waste of time | Always have concrete next steps |
| Unrealistic actions | Never completed | Scope to achievable tasks |
| No follow-up | Actions forgotten | Track in ticketing system |
Best Practices
Do's
- Start immediately - Memory fades fast
- Be specific - Exact times, exact errors
- Include graphs - Visual evidence
- Assign owners - No orphan action items
- Share widely - Organizational learning
Don'ts
- Don't name and shame - Ever
- Don't skip small incidents - They reveal patterns
- Don't make it a blame doc - That kills learning
- Don't create busywork - Actions should be meaningful
- Don't skip follow-up - Verify actions completed
