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+```mermaid
+sequenceDiagram
+    participant User
+    participant PaymentGateway
+    participant TransactionDB
+    User->>PaymentGateway: Initiate Payment
+    alt Successful Payment
+        PaymentGateway-->>TransactionDB: Store Transaction
+        TransactionDB-->>PaymentGateway: Confirm Transaction Stored
+        PaymentGateway-->>User: Payment Successful
+    else External Failure
+        PaymentGateway-->>User: Payment Gateway Error
+    else DB Failure
+        PaymentGateway-->>User: Payment Processing Error
+        TransactionDB-->>PaymentGateway: DB Error Occurred
+    end
+    opt Commit Transaction
+        TransactionDB-->>User: Commit Success
+    end
+    opt Rollback Transaction
+        TransactionDB-->>User: Rollback Success
+    end
+```
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