It takes something like half of a second for my Apple Pay Amex/Visa to let me through the barrier in the London Underground, and the complexity they have to deal with for fare calculations is quite something too.
The fare isn’t calculated on the spot though, a base amount is authorized and then only charged later.
Not that the plug needs to figure that out immediately but it’s worth noting.
This is true. Apple Pay has been something we're keen on adding