In South Africa I notice this difference all the time where the big supermarket chains seem to be near instantaneous while small stores are 10+ seconds.
I'm certain it's because the big store's card machines have a wired network connection to a router with a fibre connection, while most smaller shops just use card machines with integrated GPRS wireless modems as they even show feedback about connecting as you tap your card.
A stall vendor who I use somewhat regularly warned me one time that her card machine was down (I guess some kind of maintenance as it was earlyish on a Sunday morning) so would only be able to accept cash. I helped her put the card machine on a nearby shop's free WiFi and not only did it work around the problem, but it made card transactions going forward significantly faster.
I'm certain it's because the big store's card machines have a wired network connection to a router with a fibre connection, while most smaller shops just use card machines with integrated GPRS wireless modems as they even show feedback about connecting as you tap your card.
A stall vendor who I use somewhat regularly warned me one time that her card machine was down (I guess some kind of maintenance as it was earlyish on a Sunday morning) so would only be able to accept cash. I helped her put the card machine on a nearby shop's free WiFi and not only did it work around the problem, but it made card transactions going forward significantly faster.