Black Friday. The bank stops answering. The shopper is at the till.

transcript

Black Friday. The shopper taps. And the bank stops answering. Approve? Decline? Keep waiting? You have about one second.

A normal day: the issuer answers in about 200 milliseconds. Your budget for the issuer, every attempt included? About one second. On Black Friday, one issuer climbs to 5 seconds.

Wait? Five seconds at the till. Shoppers abandon. Merchants lose sales. Decline everything? Every honest card at that bank fails. And the shopper did nothing wrong.

So spend the second in tiers. The issuer's primary endpoint gets 500 milliseconds. Silent? A backup endpoint gets 300. Still silent? Stand-in, with 200 left. The network decides. But here's the catch. Only on rules the issuer agreed in advance.

Rules like: up to 500 dollars a transaction. 2,000 a day. A risk score of 80 or less. And the card isn't reported lost or stolen.

Every stand-in decision is queued. The issuer reconciles it later. And it accepts liability for approvals within its rules. The shopper gets an answer. The risk stays bounded.

The bank went quiet. The till still got an answer in time. Degrade, don't stop.

Full breakdown in the lecture.