How Does UPI Actually Work Behind the Scenes?

Most of us use UPI every day.

We scan a QR code, enter a PIN, and within a few seconds, the payment is complete.

But have you ever wondered what actually happens between tapping Pay and seeing Payment Successful?

There are several systems working together behind the scenes:

• How your UPI ID is resolved to the correct bank
• Why your payment app never sees your actual UPI PIN
• How NPCI routes transactions between banks
• How debit and credit happen almost simultaneously
• The security mechanisms that protect every transaction

I recently did a deep dive into the complete payment flow—from NEFT, RTGS, and IMPS to the architecture that powers modern UPI payments.

If you're interested in fintech, distributed systems, backend engineering, or payment infrastructure, you might find it interesting.

👉 Read the full article here:

http://medium.com/p/eb3632d8c021

I'd also love to hear your thoughts:

• What part of UPI's architecture surprised you the most?
• Are there other large-scale distributed systems you'd like to see broken down in a similar way?