Retry Logic Can Double-Charge Customers Without Idempotency Keys, Developer Warns

A developer article describes how a payment retry after a timeout can charge a customer twice. The first request may succeed on the payment service while only the response is lost, so retrying sends a second charge. The author proposes using an idempotency key tied to the order ID so the provider returns the original result instead of charging again. The fix only works if the payment provider properly supports idempotency. The piece argues that passing tests and clean logs do not guarantee that real-world failure conditions have been considered.