> Walmart is currently trialing it to save $3B-$7B a year in interchange fees. No crypto, just XML messages through a mainframe at the Federal Reserve with a 20 second SLA.

Please tell your user that this SLA is much too high for many purposes. A cafe or such would lose a ton of money if every transaction took 20 seconds longer to conduct.

Works fine based on the evidence. It’s a maximum SLA, not every transaction. The economics are too compelling to ignore. Fast enough.