The real question is how long can some of the smaller banks' datacenters stay up.
Lest also forget the Crowdstrike drama where many supermarkets simply went dark, in some instances for nearly 24 hours, despite working communication links. But I digress.
Literally true. However:
- If it takes them 10 minutes to fire up the generator, then 5 minutes to restart the network and registers, that is no big issue (in a many-hour outage)
- At least in my part of the USA, many supermarkets do have generators - because storm damage causes local outages relatively often, and they'd lose a lot of money if they couldn't keep their freezers and refrigerators powered. Since the power requirements of the lighting and registers are just (compared to the cooling equipment) a rounding error, those are also on generators.
Seen it done in USA, for a Target next to a Kroger grocer. Kroger lost everything that needed cold after reserve either ran out or wouldn't start, but Target had a contingencies contract and lost no product.
But both major supermarkets nearby worked on diesel generators and payment by card worked flawlessly. I guess they had satellite connection.
It might have been more complicated in small villages but people living in rural areas ually still use a lot of cash.
However I assume this can work offline with the data being uploaded later though, as basically all the small supermarkets and shops were still open here (_incredibly_ chaotic though), and on the big supermarkets card payments were working (TBF, even the free wifi was working there, I guess they probably have some satellite connection).