I’m used to the dialup-style delays but these are longer and happen at places with new equipment and high transaction volume, and they seemed to be doing real-time transactions before because even the magstripe transactions would immediately trigger the push notification to my phone.
I’ve been assuming this is some new, unoptimized codepath kludged into a legacy system because it’s very common but doesn’t seem to affect new products – e.g. Square systems are always a fraction of a second.
The one part I can’t explain is why at the subset of places which support both NFC and chips, the NFC transactions are at least as fast as magstripe when the chip transactions are so much slower.
As far as I had assumed (don't have any in-depth knowledge though), all chip systems required a challenge response with a server, so this couldn't be batched I don't think.
I can imagine it being related to internet connection speed if it was a minor delay, but people seem to describe really significant delay, even in major US cities where you'd imagine that shouldn't be a problem.
E.g. at Aldi here (Southern Germany) paying with card including entering the PIN isn't really slower than paying cash (and the Aldi cashiers are crazy fast in handling cash). At other stores the card terminals seem awfully slow, though.