diff --git a/.forge/iss-d0bdbb1b07fc-attempt-2-run-11c166a4a0e1.md b/.forge/iss-d0bdbb1b07fc-attempt-2-run-11c166a4a0e1.md
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+# iss-d0bdbb1b07fc-attempt-2-run-11c166a4a0e1
+
+Forge 이슈 작업 브랜치 `forge/iss-d0bdbb1b07fc-attempt-2-run-11c166a4a0e1`.
diff --git a/docs/architecture/transaction-sequence.md b/docs/architecture/transaction-sequence.md
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+---
+# 결제 전환 아키텍처
+
+## 트랜잭션 시퀀스 다이어그램
+
+```mermaid
+sequenceDiagram
+    participant User
+    participant PaymentGateway
+    participant Database
+    participant Application
+
+    User->>Application: 결제 요청
+    Application->>Database: 트랜잭션 시작
+    Application->>PaymentGateway: 결제 요청
+    alt 정상 흐름
+        PaymentGateway-->>Application: 결제 성공
+        Application->>Database: 트랜잭션 커밋
+        Database-->>Application: 커밋 완료
+        Application-->>User: 결제 완료
+    else 외부 실패
+        PaymentGateway-->>Application: 결제 실패
+        Application->>Database: 트랜잭션 롤백
+        Database-->>Application: 롤백 완료
+        Application-->>User: 결제 실패
+    else DB 실패
+        Application->>Database: 트랜잭션 롤백
+        Database-->>Application: 롤백 실패
+        Application-->>User: 시스템 오류
+    end
+```
+
+## 주의사항
+- 외부 결제 gateway는 port interface 뒤에 두고 domain에서 adapter를 직접 참조하지 않는다.
+---
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