Another great B2B story - Stripe (online payments):
“Businesses that deferred moving online or had no reason to operate online have made the leap practically overnight,” says John Collison, co-founder and president of Stripe.
Also, this London-based identity/compliance startup seems to be doing well with facial recognition (convolutional neural nets) and, I guess, SQL databases storing your gov data:
Among B2C fintechs, I see Square with its Cash App as fast-moving megatrain - payments (B2B) with hardware and software solutions, wealth management (banking, stock trading, bitcoin trading, etc). PayPal with Venmo are also hot but they are an established entity and PayPal seems bloated and “old-school” (it probably still has some of Musk and co.'s code in its repos).
Timeless advice for this century in one book: