[gkoberger]

If my credit card failed one out of every 20 transactions (95%), I still wouldn't use it. At a restaurant, you'd be stuck having consumed the food but with no way to pay for it.

[lettergram]

I work at a bank, we have the minimum of 5 9's rule for every app and transactional entity. Basically, it needs to be up 99.999% of the time.

Currently, we have a 99.9998% uptime for the main transactional cluster/mainframe/computer/etc. and that still means 20 minutes of down time in the last 20 years.

That doesn't sound like a lot, but that's like ~$1 million of transactions lost for every minute it is down.

[pbreit]

That's kinda baloney. Reality is that a minute or 2 of downtime will result in much less than a total loss because people just wait and retry.

[lettergram]

You can't wait at a register... people will try swapping the card 2 times (maybe 3).