Those are enterprise services that offer at least four nines of availability each, probably more. AWS even advertises 11 nines for a select set of features. The

Those are enterprise services that offer at least four nines of availability each, probably more. AWS even advertises 11 nines for a select set of features. They should add up to a service that has an availability in the 99.98%. Meanwhile, obtaining anything over 99.9% is usually a challenge for the amateur. Even if you are on call on every day of the year, it's very easy to go to sleep with your phone muted and wake up the next morning to discover the service is down for whatever reason.