The gold standard of availability is generally "four nines" - 99.99%. To me: 99.5% (or less) = unacceptable 99.9% = average 99.99% = exceptional 0.5% downtime

The gold standard of availability is generally "four nines" - 99.99%. To me: 99.5% (or less) = unacceptable 99.9% = average 99.99% = exceptional 0.5% downtime = 216 mins/month (almost an hour a week!) 0.1% downtime = 43.2 mins/month 0.01% = 4.32 mins/month Getting to that last level is certainly very hard, I hope Heroku will get there, but the service is relatively new, fairly cutting edge, under active development, etc. I would not entirely expect them to reach "four nines", but I hope it is their goal.