The right comparison for Nasdaq's order processing volume or messaging volume would be India's National Stock Exchange (NSE). It does more executed orders per day than nasdaq.

I worked on scaling UPI a few years ago. Real-time Payments is vastly more complex as it is much more distributed - each transaction involves the two banks holding funds, two end-user apps (and their banks), and the network (npci) – for the payment to complete end to end, multiple message exchanges need to happen between these parties while the user at both ends are waiting. So, if you measure the scale in messages/sec it would 10-25x higher.

Real-time payment rails that works 24/7 365 days a year from any bank to any bank (domestic, no exceptions) for free is truly a game-changer. Compare that to US payment rails which is slow and expensive. Apart from UPI, India has 3 more payment rails – NEFT (similar to ACH – batch settlement), IMPS (similar to UPI, instantaneous - but different user experience), RTGS (real-time, intermediated by the central bank RBI, but only for high-value transactions) – all are 24/7/365 and free. Then, there's credit card rails – apart from Visa and Mastercard, India also has RuPay which has much lower interchange rate.