Postmortem Standards

Scope: Technical/engineering incident postmortem templates, methodologies, and best practices Load if: Conducting incident postmortems, writing postmortem reports, establishing postmortem processes, incident response workflows, post-incident analysis Prerequisites: None (standalone guideline)

Postmortems are structured reviews after incidents to understand what happened, why it happened, and how to prevent recurrence. Principles: blameless culture (systems, not people), learning focus, timely execution (48-72 hours), actionable outcomes (action items with timelines).

Core Principles

• MUST maintain blameless culture - focus on systems, processes, and contributing factors, not individual fault
• MUST be conducted within 48-72 hours of incident resolution
• MUST invite all key participants (incident commander, responders, affected teams) — proceed at the scheduled time with the available core group, and collect input from anyone who couldn't attend asynchronously; don't let one person's unavailability stall the 48-72 hour window
• MUST result in specific, assigned action items with timelines
• MUST be shared widely within the organization for learning
• Attribute failures to systems and processes, not individuals or teams
• Conduct postmortems per the severity/impact criteria in Best Practices > When to Conduct below (not every incident by default) — minor incidents still warrant one when they reveal systemic issues, recur, or affect customers
• Give every action item an owner and a timeline

Report Structure

Include these sections in order:

1. Incident Summary

Include: title, ID, date, duration (ISO 8601 time range), severity (P0/P1/P2), brief description (2-3 sentences), key metrics (downtime, affected users, error rates)

2. Impact Assessment

Include: customer impact (users, regions, services), business impact (revenue, SLA violations, reputation), technical impact (degradation, data loss, performance), duration

3. Timeline

Include: discovery time/method, key events chronologically (local timezone, ISO 8601), response actions, resolution time, post-resolution verification

YYYY-MM-DDTHH:MM:SS±HH:MM - Alert triggered: «Alert description»
YYYY-MM-DDTHH:MM:SS±HH:MM - On-call engineer paged, investigation started
YYYY-MM-DDTHH:MM:SS±HH:MM - Root cause identified: «Root cause description»
YYYY-MM-DDTHH:MM:SS±HH:MM - Mitigation applied: «Mitigation action»
YYYY-MM-DDTHH:MM:SS±HH:MM - Service restored, monitoring confirmed normal operation

4. Root Cause Analysis

Include: primary root cause, contributing factors (system design, process gaps, monitoring gaps, documentation gaps, training gaps, environmental factors), analysis methodology (Five Whys, fishbone diagram, timeline analysis), evidence/data

5. Resolution Steps

Include: immediate mitigation actions, long-term fixes, verification steps, rollback procedures (if applicable)

6. Action Items

Include: ID, description, owner (individual or team), priority (P0/P1/P2 or High/Medium/Low), target completion date, success criteria

Tracking: Use structured lists, issue trackers, or project management tools.

7. Lessons Learned

Include: what went well, what could be improved, process improvements, tooling improvements, knowledge gaps

8. Communication Plan

Include: internal notifications, customer communications (if applicable), status page updates, post-incident review meetings, documentation updates

Root Cause Analysis Methodologies

Five Whys Technique

Ask "why" five times to drill down to root cause:

1. Why did the service fail? → «Immediate cause»
2. Why «immediate cause»? → «Underlying cause»
3. Why «underlying cause»? → «Deeper cause»
4. Why wasn't this caught? → «Detection gap»
5. Why «detection gap»? → «Root cause»

Fishbone Diagram (Ishikawa)

Categorize contributing factors:

• People: training, knowledge, communication
• Process: procedures, workflows, documentation
• Technology: tools, systems, infrastructure
• Environment: external factors, dependencies

Timeline Analysis

Identify: trigger events, cascade failures, response delays, resolution bottlenecks

Best Practices

When to Conduct

• MUST conduct for all P0/P1 incidents (critical/high severity)
• SHOULD conduct for P2 incidents (medium severity) if they reveal systemic issues
• SHOULD conduct for recurring incidents even if individually low severity
• SHOULD conduct for incidents with customer impact

Participants

Required: Incident commander, primary responders, on-call engineers involved, team leads from affected systems, product/engineering managers (if customer impact)

Optional: SRE/DevOps team members, security team (if security-related), customer support (if customer impact), executive stakeholders (for high-severity incidents)

Timeline for Completion

• 24 hours: Initial incident summary, impact assessment, basic timeline reconstruction
• 48-72 hours: Complete postmortem document, root cause analysis, initial action items identified
• 1-2 weeks: Action items assigned and prioritized, follow-up review meeting scheduled, documentation updates completed

Sharing and Documentation

• MUST publish postmortem in accessible location (wiki, documentation system)
• MUST share with all engineering teams
• MUST include in team retrospectives and learning sessions
• MUST update runbooks and documentation based on learnings
• MUST track action items to completion

Blameless Language

Core principle: Focus on systems, not people. Incidents are system failures; blame prevents learning.

Guidelines: Use "we" not "they". Focus on "what" and "why" not "who".

Avoid

• "«Person» deployed broken code" - assigns blame

Good

• "The deployment process allowed code with a connection leak to reach production" - describes system gap

Before You Finish

When conducting postmortems:

1. Schedule within 48-72 hours of incident resolution
2. Include all key participants (incident commander, responders, affected teams)
3. Follow 8-section structure (Summary → Impact → Timeline → Root Cause → Resolution → Action Items → Lessons → Communication)
4. Use Five Whys or fishbone diagram for root cause analysis
5. Assign owners and timelines to all action items
6. Share widely for organizational learning

Related

• @smith-clarity/SKILL.md - Root cause analysis techniques (Five Whys, fishbone)
• @smith-validation/SKILL.md - Hypothesis testing