diff --git a/.forge/iss-478981daa4be-attempt-1-run-c0b7e9d69a7a.md b/.forge/iss-478981daa4be-attempt-1-run-c0b7e9d69a7a.md
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+# iss-478981daa4be-attempt-1-run-c0b7e9d69a7a
+
+Forge 이슈 작업 브랜치 `forge/iss-478981daa4be-attempt-1-run-c0b7e9d69a7a`.
diff --git a/docs/architecture/transaction-sequence.md b/docs/architecture/transaction-sequence.md
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+```mermaid
+sequenceDiagram
+    participant User
+    participant PaymentGateway
+    participant Database
+
+    %% 정상 흐름 %%
+    User->>PaymentGateway: 결제 요청
+    PaymentGateway->>User: 결제 승인
+    User->>Database: 거래 기록 저장
+    Database-->>User: 거래 성공
+    %% 커밋 %%
+    User->>Database: 커밋
+    Database-->>User: 커밋 완료
+
+    %% 외부 실패 %%
+    User->>PaymentGateway: 결제 요청
+    PaymentGateway-->>User: 결제 실패
+    %% 롤백 %%
+    User->>Database: 롤백
+    Database-->>User: 롤백 완료
+
+    %% DB 실패 %%
+    User->>PaymentGateway: 결제 요청
+    PaymentGateway->>User: 결제 승인
+    User->>Database: 거래 기록 저장
+    Database-->>User: DB 오류
+    %% 롤백 %%
+    User->>Database: 롤백
+    Database-->>User: 롤백 완료
+```
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