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+```mermaid
+sequenceDiagram
+    participant User
+    participant Controller
+    participant Service
+    participant Repository
+    participant Database
+
+    User->>Controller: 결제 요청
+    Controller->>Service: 결제 처리 요청
+    Service->>Repository: 데이터 저장 요청
+    Repository->>Database: DB 저장 요청
+    Database-->>Repository: 저장 완료
+    Repository-->>Service: 저장 완료
+    Service-->>Controller: 처리 완료
+    Controller-->>User: 결제 완료
+
+    alt 외부 실패
+        Service-->>Controller: 실패 응답
+        Controller-->>User: 결제 실패
+    end
+
+    alt DB 실패
+        Repository-->>Service: DB 오류
+        Service-->>Controller: 처리 실패
+        Controller-->>User: 결제 실패
+    end
+
+    Note over Service, Repository: Commit/rollback 경계 설정
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