How? By magic dust sprinkled by Docker Inc?

> When the host machine goes down, the scheduler will pretty quickly start the container on a new machine. There the container will startup much quicker than a VM would.

You seem to forget that a) container's filesystem needs to be downloaded in the first place, and b) that VMs can work in a standby mode, not running the service (database) when not needed. Starting a container seems to be much more fragile solution.

There are already well-developed mechanisms for things like that, and we (sysadmins) were using them for dozens years already.

The question still stands: what do containers do better than the mechanisms we had for a long time?