diff --git a/.forge/iss-d65d495e8095-attempt-2.md b/.forge/iss-d65d495e8095-attempt-2.md
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+++ b/.forge/iss-d65d495e8095-attempt-2.md
@@ -0,0 +1,3 @@
+# iss-d65d495e8095-attempt-2
+
+Forge 이슈 작업 브랜치 `forge/iss-d65d495e8095-attempt-2`.
diff --git a/docs/architecture/transaction-sequence.md b/docs/architecture/transaction-sequence.md
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+%%%{init: {'themeVariables': {'sequenceDiagramTheme': 'default'}}}%%%
+
+sequenceDiagram
+    participant User
+    participant PaymentGateway
+    participant Database
+
+    User->>PaymentGateway: Initiate Payment
+    alt Successful Payment
+        PaymentGateway->>Database: Commit Transaction
+        Database-->>PaymentGateway: Confirm Commit
+        PaymentGateway-->>User: Payment Success
+    else External Failure
+        PaymentGateway-->>User: Payment Failure
+    else DB Failure
+        PaymentGateway->>Database: Rollback Transaction
+        Database-->>PaymentGateway: Confirm Rollback
+        PaymentGateway-->>User: Payment Rollback
+    end
\ No newline at end of file