India's UPI (digital payments) is almost as big a scale as it gets, and it's pretty universally considered a success: https://en.wikipedia.org/wiki/Unified_Paym

India's UPI (digital payments) is almost as big a scale as it gets, and it's pretty universally considered a success: https://en.wikipedia.org/wiki/Unified_Payments_Interface https://en.wikipedia.org/wiki/Unified_Payments_Interface