UPI Payments & Reconciliation

Invoices are paid by UPI through a bank’s API. On the customer’s screen, a payment can look failed while the money has in fact arrived, and asking that customer to pay again risks collecting twice.

I led the integration across the Django backend and the React billing interface.

• Payment notifications arrive from outside the system, so each one has to be authenticated before it is trusted.
• The same event can be delivered more than once and must not change billing state twice.
• An uncertain outcome is not a failure, and the customer should not be pushed to retry until it is resolved.

• A React billing interface on top of Django REST APIs.
• Payment requests created from invoices, with payment status driven by bank webhooks.
• Signature verification on incoming webhooks before any state changes.
• Idempotent event handling, so a repeated notification cannot be applied twice.
• A reconciliation step for uncertain outcomes that runs before a new payment is requested.

Retrying straight away feels faster to the customer but risks a second collection. Reconciling uncertain outcomes first adds a short wait in rare cases and keeps billing state honest.

The workflow tells a failed payment attempt apart from money actually received, which lowers the risk of collecting twice or asking for unnecessary retries.