A few months ago, Australia’s second biggest ISP died for a few hours. Retailers tied to their network were unable to process non-cash transactions.
Months ago, in Singapore, similarly a single relatively small server farm had issues, blocking for a long time a very large number of transactions. (Some details at: https://www.channelnewsasia.com/commentary/dbs-digibank-payl... ) The news outlets in Singapore then commented: please, as these things can always happen, do not forget to bring some cash with you...
Canada's payment network had an outage for over an hour last year, 2023 Sep 23. see https://www.cbc.ca/news/canada/moneris-network-outage-1.6976...