Earlier quoted context omitted.
Nah, too complex. Just use BLE with an app and this will unlock the cart. Very low friction and it does the cart customer matching. And make usage of carts mandatory ( door will not open.... )
Go on, go on! I feel we are on to something!
But only one reserve I have: the carts have to be powered for connectiviy and the electric unlock mechanism. So they could be more expensive. But then let's add an ad screen ( E-Ink! ) on the front inside and have this solve the increase.