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+```mermaid
+sequenceDiagram
+    participant User
+    participant Service
+    participant Repository
+    participant PaymentGateway as PG
+
+    User->>Service: 결제 요청
+    Service->>Repository: 결제 정보 저장
+    alt 결제 성공
+        Service->>PG: 결제 요청
+        PG-->>Service: 결제 성공 응답
+        Service-->>User: 결제 완료 응답
+    else 외부 실패
+        Service-->>User: 결제 실패 응답
+    else DB 실패
+        Service->>Repository: 롤백 요청
+        Repository-->>Service: 롤백 완료
+        Service-->>User: 결제 실패 응답
+    end
+```