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+```mermaid
+sequenceDiagram
+    participant User
+    participant PaymentService
+    participant PaymentGateway
+    participant Database
+
+    User->>PaymentService: 결제 요청
+    PaymentService->>Database: 거래 시작
+    Database-->>PaymentService: 거래 ID
+    PaymentService->>PaymentGateway: 결제 진행
+    alt Success
+        PaymentGateway-->>PaymentService: 결제 성공
+        PaymentService->>Database: 거래 확정
+    else Failure
+        PaymentGateway-->>PaymentService: 결제 실패
+        PaymentService->>Database: 거래 롤백
+    end
+```
\ No newline at end of file