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Abstract The Unified Payments Interface (UPI) is one of the most successful real-time payment systems ever deployed at national scale. While it appears simple at the user interface level, UPI is fundamentally a high-throughput, fault-tolerant, distri...

While paying via Paytm, I noticed a small “+” button on the payment keypad. That’s it. No tooltip. No announcement. No onboarding. Yet it solved a problem I’ve silently lived with for years. Earlier, paying for multiple items meant: Switch to calcula...
