The Unified Payments Interface (UPI), which has revolutionized retail digital payments in India by enabling real-time bank-to-bank transfers via mobile, was developed and is operated by the ___.

Answer: NPCI (or National Payments Corporation of India)

NPCI is an umbrella organization for operating retail payments and settlement systems in India, initiated by the RBI and the Indian Banks' Association (IBA). UPI's architecture allows multiple bank accounts to be accessed through a single mobile application, merging the seamless features of wallets with the security and direct settlement of traditional banking networks.