Preventing Lost Revenue in Payment Flows
Payment gateway integration is the most mission-critical code in an e-commerce platform. If an integration mishandles bank server timeouts, duplicate charges occur, orders are lost, and angry customers demand refunds.
Critical Engineering Safeguards:
1Always Verify Webhook Cryptographic Signatures: Never mark an order as "Paid" solely based on frontend browser callbacks. Always verify the HMAC SHA-256 signature sent by Razorpay or Cashfree to your secure backend webhook endpoint.
2Idempotency Keys for Duplicate Protection: When submitting orders or refund requests, pass a unique idempotency key so that accidental double-clicks by anxious buyers never charge them twice.
3Graceful Handling of Pending UPI Transactions: If an issuing bank delays confirmation, set the order status to "Payment Pending" and poll the gateway status API asynchronously rather than failing the transaction.