docs(10_Wiki): Topic_Business/General/Graphic/Programming을 Topics/ 하위로 이동
최상위 10_Wiki/Topic_*였던 4개 카테고리 폴더를 10_Wiki/Topics/Topic_* 로 재배치. 콘텐츠 변경 없음(순수 폴더 이동) — Topics/ 하위 나머지 폴더는 이미 지난 커밋에서 전부 정리된 상태(잔존 항목은 에이전트 운영 상태 및 사용자가 보존을 요청한 업데이트0615/무제 3.canvas 뿐).
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id: wiki-2026-0508-lessons-learned
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title: Lessons Learned
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category: 10_Wiki/Topics
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status: verified
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canonical_id: self
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aliases: [Postmortem, Retrospective, After-Action Review]
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duplicate_of: none
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source_trust_level: A
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confidence_score: 0.9
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verification_status: applied
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tags: [process, postmortem, learning, sre]
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raw_sources: []
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last_reinforced: 2026-05-10
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github_commit: pending
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tech_stack:
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language: n/a
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framework: n/a
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---
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# Lessons Learned
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## 매 한 줄
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> **"매 institutionalized regret-into-knowledge transformer"**. 매 1940s US Army After-Action Review (AAR) 의 origin → 매 2003 Google SRE 의 blameless postmortem 의 modern form. 매 each incident 매 paid-for data; throwing it 매 paying twice.
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## 매 핵심
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### 매 mechanism
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1. Incident / project ends.
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2. Timeline 매 reconstructed.
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3. Root causes (plural) 매 identified.
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4. Action items 매 owned + scheduled.
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5. Doc 매 published, indexed, re-read.
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### 매 modern best practices (Google SRE)
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- **Blameless** — 매 systems 매 fail, not people.
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- **Concrete action items** with owners + due dates.
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- **5 Whys** or **Causal Analysis using STAMP** (no single root cause).
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- **Public** within org (searchable).
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### 매 응용
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1. Production incidents (PagerDuty integration).
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2. Project retros (sprint, quarter).
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3. Security incidents (legal-friendly variant).
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## 💻 패턴
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### Postmortem template (Google SRE-style)
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```markdown
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# Incident YYYY-MM-DD: <short title>
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## Summary
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1-2 sentences.
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## Impact
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- Users affected: ...
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- Duration: ...
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- Revenue: ...
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## Root causes (plural)
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1. ...
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2. ...
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## Trigger
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What event started the incident.
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## Resolution
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What stopped it.
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## Detection
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How we knew (and how late).
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## Timeline (UTC)
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| Time | Event |
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|---|---|
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| 14:32 | Deploy started |
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| 14:34 | Error rate spike |
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| ... | ... |
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## What went well
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- ...
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## What went poorly
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- ...
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## Where we got lucky
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- ...
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## Action items
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| ID | Action | Owner | Due | Type |
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|---|---|---|---|---|
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| AI-1 | Add canary deploy | @alice | 2026-05-20 | prevent |
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| AI-2 | Improve alert | @bob | 2026-05-15 | detect |
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```
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### Action item tracker (GitHub-issue export)
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```bash
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gh issue create \
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--title "AI-1: Add canary deploy" \
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--label "postmortem,prevent" \
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--assignee alice \
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--milestone "Q2 2026"
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```
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### 5 Whys (causal chain)
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```
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Why did the site go down? Server OOM.
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Why OOM? Cache grew unbounded.
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Why unbounded? No eviction policy.
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Why no policy? PR review missed it.
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Why missed? Checklist had no cache item.
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→ Root: missing checklist item (process), not the engineer.
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```
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### Aggregation across postmortems (yearly review)
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```sql
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SELECT root_cause_category, COUNT(*) AS n, SUM(downtime_minutes) AS total_dt
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FROM postmortems
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WHERE date >= '2025-01-01'
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GROUP BY root_cause_category
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ORDER BY total_dt DESC;
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```
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### Embedded retro into sprint
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```markdown
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- ✅ Did → keep
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- 🔄 Did → improve
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- ❌ Did → stop
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- 💡 Didn't → start
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```
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## 매 결정 기준
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| 상황 | Format |
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|---|---|
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| Production incident | Google SRE postmortem |
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| Sprint end | Sailboat / Start-Stop-Continue |
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| Project end | After-Action Review |
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**기본값**: Blameless, concrete action items, public, re-read at 30 days.
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## 🔗 Graph
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- 부모: [[SRE]]
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- 변형: [[After-Action-Review]]
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## 🤖 LLM 활용
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**언제**: post-incident, project end, security event.
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**언제 X**: trivial bug fix (use commit message instead).
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## ❌ 안티패턴
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- **Blame culture**: 매 hides root causes.
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- **No follow-through on action items**: 매 same incident again.
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- **Single root cause**: 매 systems-thinking 매 missed.
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- **Document then forget**: 매 unread postmortem 매 worthless.
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## 🧪 검증 / 중복
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- Verified (Google SRE Book Ch. 15; Etsy "blameless postmortem" essay; US Army AAR doctrine).
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- 신뢰도 A.
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## 🕓 Changelog
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| 날짜 | 변경 |
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|---|---|
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| 2026-05-08 | Phase 1 |
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| 2026-05-10 | Manual cleanup — Lessons Learned FULL with SRE template |
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