Earlier quoted context omitted.
It's experience in the two examples I gave : I singlehandedly built my company : RAMM Science ( https://ramm.science ) And he singlehandedly built one of Europes largest online betting system backends (and scaled it to 800 transactions a second using Deep Learning, Kafka and a Hadoop cluster)
Is 800 transactions per second good? It seems like a low number but what do I know. I am impressed that Europe's largest betting system only does 800 transactions per second.
The frontends (where the casino / betting games run) do a lot more than this, but they work against the balance in the account, it's the payment gateway that's doing 800/s