What's the minimum time counted for billing in Heroku?

Question

Ec2 instance hour calculated by hour by hour. If you just start and close an instance, it still counted as one hour.

How Heroku handle this? By Minute or By Hour?

Lets assume my app usage exceeds 750 Free Dyno Hour Limit

Answer 1

Heroku prorata to the second. A dyno costs $0.05 per hour. So if you go over 750 hours you will be charged at $0.05 per hour or $0.000833333 per minute. In fact, pretty much all addons also follow the same billing model too.

You can read about billing and charges as https://devcenter.heroku.com/articles/usage-and-billing#cost