The per-minute billing is an advantage when you are scaling up and down rapidly. If you use VMs just for 5 minutes, per minute pricing is 20x cheaper than hourl

The per-minute billing is an advantage when you are scaling up and down rapidly. If you use VMs just for 5 minutes, per minute pricing is 20x cheaper than hourly billing. However with a database it is rare to scale up and down rapidly. Rather you expect change over the order of days. Imagine you go from 10 instance to 15 instances over a week. per minute billing only saves a possible 5 instance-hours over the week compared to hourly billing, which is less than 1% saving.