2864. API idempotency: Insert a payment request only once by a unique idempotency key. — C# ASP.NET + ADO.NET

DBMS Published 30 Sept 2026 Updated 30 Sept 2026 0 Views Verified

In a api idempotency module, solve this as a production problem using C# ASP.NET + ADO.NET: Insert a payment request only once by a unique idempotency key. Provide the SQL, explain the logic, show safe application integration, and mention failure/edge cases.

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Answer & Explanation

4 Answers

Verified Correct Answer

Option A

INSERT INTO payments(idempotency_key,order_id,amount,status) VALUES(:key,:order_id,:amount,'pending') ON DUPLICATE KEY UPDATE id=id;

Additional Explanation

The unique key makes retries safe; the no-op update returns the existing row path without creating a duplicate.

Verified

Option B

SELECT * FROM table_name;

Additional Explanation

Incorrect: it does not satisfy the stated business rule and can return/change unintended data.

Verified

Option C

DELETE FROM table_name;

Additional Explanation

Incorrect: it does not satisfy the stated business rule and can return/change unintended data.

Verified

Option D

UPDATE table_name SET status='active';

Additional Explanation

Incorrect: it does not satisfy the stated business rule and can return/change unintended data.