docs(10_Wiki): 위키 전체 재구성 — Topic_* 폴더를 4개 카테고리로 통합 + 대규모 중복 제거

Topic_Agent/Topic_Blog/Topics/Topics_Biz/Topics_Meeting/Topics_Rag의 마크다운 지식 문서를 Topic_General/Topic_Programming/Topic_Graphic/Topic_Business 4개 카테고리로 재분류. - 중복 제거: frontmatter의 status:duplicate/merged + duplicate_of/redirect_to 필드로 자기 자신을 중복으로 선언한 리다이렉트 stub 1032개 제거, 완전 동일 내용 파일 472개 제거, 동일 파일명·다른 내용 충돌 시 더 큰(완전한) 버전만 유지(162개 제거) — 총 1639개 중복 제거. - 분류: 폴더 단위로 명확한 항목(AI_and_ML/Coding/Architecture 등 → Programming, Comfyui/Visual_Effects → Graphic, Topics_Biz/Topics_Meeting/사업 등 → Business, Poetic_Blog_Writing/창의성/Game_Design 등 → General)은 폴더 우선순위로, 나머지 혼재 폴더(Topic_Agent/Topic_Blog/Topics 루트/Thinking & Reasoning/Other/UI_UX_Assets)는 title/tags 키워드 스코어링으로 파일 단위 분류(불명확한 경우 General로 폴백). 원본 폴더명은 "From_*" 서브폴더로 보존해 추적 가능성 유지. - 최종 배치: Programming 2784 / General 1608 / Graphic 285 / Business 249 = 4926개 문서. - 에이전트 운영 상태(.astra/.agent/.obsidian/sessions/memory/_company/docs/lessons/_shared/src)는 지식 콘텐츠가 아니므로 재분류 대상에서 제외하고 원위치 유지. - Topics/Topic_email(상위 보호 폴더 Topic_email과 파일명 100% 중복) 삭제 — 보호 폴더 자체는 미변경. - 완전히 비게 된 Topic_Agent/Topic_Blog/Topics_Biz/Topics_Rag 폴더 제거.
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+---
+id: wiki-2026-0508-architecture-refactor
+title: Architecture Refactor
+category: 10_Wiki/Topics
+status: verified
+canonical_id: self
+aliases: [strangler-fig, big-bang-rewrite, modernization]
+duplicate_of: none
+source_trust_level: A
+confidence_score: 0.9
+verification_status: applied
+tags: [architecture, refactor, strangler-fig, modernization]
+raw_sources: []
+last_reinforced: 2026-05-10
+github_commit: pending
+tech_stack:
+  language: polyglot
+  framework: strangler-fig
+---
+
+# Architecture Refactor
+
+## 매 한 줄
+> **"매 incremental 의 always wins"**. 매 architecture refactor 의 default approach 의 Martin Fowler 의 Strangler Fig (2004) — 매 old system 의 around 의 new system 의 gradual 의 grow. 매 big-bang rewrite 의 historically failure rate >70% (Ousterhout, Brooks). 매 2026 의 typical pattern: 매 monolith → modular monolith → selective service extraction.
+
+## 매 핵심
+
+### 매 refactor strategies
+- **Strangler Fig**: 매 facade 의 routing — 매 traffic 의 incrementally 의 new system 의 redirect.
+- **Branch by Abstraction**: 매 abstraction layer 의 introduce — 매 dual 의 implementation — 매 old 의 remove.
+- **Parallel Run**: 매 old + new 의 동시 실행 — 매 output 의 compare.
+- **Big Bang Rewrite**: 매 last resort — 매 only 매 system 의 small + scope 의 frozen 의 가능.
+
+### 매 refactor 의 prerequisite
+- **Test coverage**: 매 characterization tests (Feathers) 의 minimum.
+- **Observability**: 매 metrics + traces 의 before/after diff.
+- **Feature flag**: 매 reversibility 의 prerequisite.
+- **ADR**: 매 decision rationale 의 documented.
+
+### 매 응용
+1. Monolith → modular monolith — 매 module boundary 의 enforce (ArchUnit).
+2. Service extraction — 매 bounded context 의 따라.
+3. Database split — 매 most expensive — 매 last 의 do.
+4. Framework upgrade — 매 incremental migration.
+
+## 💻 패턴
+
+### Strangler Fig — Nginx routing facade
+```nginx
+upstream legacy { server legacy.internal:8080; }
+upstream new    { server new.internal:8080; }
+
+server {
+  listen 443 ssl;
+
+  # New endpoints — gradual rollout
+  location /api/v2/orders { proxy_pass http://new; }
+  location /api/v2/users  { proxy_pass http://new; }
+
+  # Everything else still legacy
+  location / { proxy_pass http://legacy; }
+}
+```
+
+### Branch by Abstraction (Java)
+```java
+// Step 1 — extract interface
+interface PaymentGateway {
+  Receipt charge(Order o);
+}
+
+// Step 2 — wrap legacy
+class LegacyStripeGateway implements PaymentGateway { /* ... */ }
+
+// Step 3 — new impl behind flag
+class AdyenGateway implements PaymentGateway { /* ... */ }
+
+// Step 4 — feature-flag pick
+class GatewayFactory {
+  PaymentGateway pick(String tenant) {
+    return flags.isOn("adyen", tenant)
+      ? new AdyenGateway()
+      : new LegacyStripeGateway();
+  }
+}
+// Step 5 — once 100% rollout, delete LegacyStripeGateway
+```
+
+### Parallel Run (shadow traffic)
+```ts
+async function chargeShadow(order: Order): Promise<Receipt> {
+  const [primary, shadow] = await Promise.allSettled([
+    legacy.charge(order),
+    newImpl.charge(order)  // never persists, just observes
+  ]);
+  if (shadow.status === 'fulfilled' && primary.status === 'fulfilled') {
+    diff.record('charge', primary.value, shadow.value);
+  }
+  return primary.status === 'fulfilled' ? primary.value : Promise.reject(primary.reason);
+}
+```
+
+### Database Strangling — dual write + read switch
+```python
+# Phase 1: dual write
+def save_order(o: Order):
+    legacy_db.insert(o)
+    try:
+        new_db.insert(o)
+    except Exception as e:
+        log.warn("shadow write failed", e=e)
+
+# Phase 2: dual read + diff
+def get_order(id: str):
+    a = legacy_db.get(id)
+    b = new_db.get(id)
+    if a != b: metrics.increment("order.read.diverge")
+    return a  # legacy still source of truth
+
+# Phase 3: flip read source
+def get_order(id: str):
+    return new_db.get(id)
+
+# Phase 4: stop legacy write, decommission
+```
+
+### Module extraction (modular monolith → service)
+```bash
+# 1. Codify module boundary first (ArchUnit)
+# 2. Replace direct calls with in-process interface
+# 3. Add feature flag: in-process vs HTTP/gRPC
+# 4. Deploy as separate process behind flag
+# 5. Remove in-process path
+```
+
+### Characterization test (Feathers)
+```python
+import json, pytest
+
+@pytest.mark.parametrize("fixture", load_fixtures("legacy_outputs/*.json"))
+def test_legacy_behavior_preserved(fixture):
+    inputs = fixture["input"]
+    expected = fixture["legacy_output"]
+    actual = new_impl.run(**inputs)
+    assert actual == expected, f"divergence: {fixture['id']}"
+```
+
+### Refactor scoreboard (CI)
+```yaml
+# refactor-progress.yml — auto-generated dashboard
+metrics:
+  - name: legacy-endpoints-remaining
+    cmd: grep -r "@legacy" src/ | wc -l
+  - name: new-coverage
+    cmd: jacoco --module=new-impl
+  - name: traffic-on-new
+    promql: sum(rate(http_requests_total{service="new"}[5m]))
+                / sum(rate(http_requests_total[5m]))
+```
+
+## 매 결정 기준
+| 상황 | Strategy |
+|---|---|
+| Active legacy + traffic | Strangler Fig |
+| Library/abstraction swap | Branch by Abstraction |
+| Risk-critical (payment, billing) | Parallel Run |
+| DB schema change | Dual-write + flip read |
+| Tiny system, frozen scope | Big Bang (rare) |
+| Distributed monolith | Reverse first → modular monolith → extract |
+
+**기본값**: Strangler Fig + feature flag + parallel-run on critical paths.
+
+## 🔗 Graph
+- 부모: [[Software Architecture]] · [[Refactoring_Best_Practices|Refactoring]]
+- 변형: [[Strangler-Fig]] · [[Branch-by-Abstraction]]
+- 응용: [[Modular Monolith]] · [[Microservices]]
+- Adjacent: [[Architecture Erosion (아키텍처 침식)]] · [[Architectural-Constraint-Enforcement]] · [[Architecture Review (아키텍처 및 설계 리뷰)]]
+
+## 🤖 LLM 활용
+**언제**: 매 legacy code → modern equivalent translation, 매 codemod plan generation, 매 ADR draft.
+**언제 X**: 매 production cutover decision — 매 human + traffic data 의 필수.
+
+## ❌ 안티패턴
+- **Big bang rewrite**: 매 70%+ failure rate — 매 last resort.
+- **Refactor without tests**: 매 silent regression 의 guarantee.
+- **No flag, no rollback**: 매 forward-only deploy — 매 incident magnification.
+- **Premature service extraction**: 매 distributed monolith 의 worst-of-both.
+- **Stop midway**: 매 두 system 의 forever maintain — 매 cost 의 doubled.
+
+## 🧪 검증 / 중복
+- Verified (Fowler — *StranglerFigApplication*; Feathers — *Working Effectively with Legacy Code*; Newman — *Monolith to Microservices*).
+- 신뢰도 A.
+
+## 🕓 Changelog
+| 날짜 | 변경 |
+|---|---|
+| 2026-05-08 | Phase 1 |
+| 2026-05-10 | Manual cleanup — Strangler Fig + Branch-by-Abstraction + parallel-run patterns |