Instant transfers have been available for many years. they were not free, but most banks supported doing them.
Zelle, previously known as clearXchange, and whatever else, but if you had an account at one of the bigger bank, it has long been trivial to send money to each other.
https://en.wikipedia.org/wiki/Zelle
> In April 2011, the clearXchange service was launched. It was originally owned and operated by Bank of America, JPMorgan Chase, and Wells Fargo.[6][7] The service offered person-to-person (P2P), business-to-consumer (B2C), and government-to-consumer (G2C) payments.[8]