The reliance on technology for convenience has tons of those kinds of situations inherent in it. No one is willing to accept the cost for ensuring the infrastructure is resilient. Many individual business (including some large chains) maintain manual credit card machines that they can use as backup, but usually that isn't why they actually have them -- it's usually because they need to do remote transactions (such as field deliveries) and know that they won't always have a suitable cell signal available.

I think the bigger weak link is the cash register in general. When I was growing up if there was a power outage most stores just continued doing business as long as there was sufficient light available. They tallied your purchases by hand and accepts cash, checks, or credit cards manually without problems and without much of a slowdown, either, because cashiers knew how to add and how to figure sales tax and how to count back change. Today, few of them could do that and, even if they did, they don't know what the price of anything is because the price isn't marked on the vast majority of items. So even if they could do the math and process the payments, the transactions would crawl to a halt while prices are looked up on the shelves. And even then, the price marked on the shelves is often not the price that you actually pay due to member discounts or specials that are only listed in flyers and such.

We have crafted a system in which we've only (by and large) looked at the whiz bang cool features and have simply assumed that everything is always going to work out nicely (and that whatever disruptions we do encounter will be very short-lived).

 

I only had to deal with one power outage and I could only service those with cash. That was in 2006. Bit of a hassle since I would have to write their purchase down and the later scan their items but luckily most of the people that did business with that store only bought on average 1.5 items(the most expensive super market in the country...). So I got home on regular time anyways

Checks haven't been accepted by anyone but banks for about 20 years here...