Those who do that don't know what they are doing (even if they outnumber the other side hundred to one, they "don't count" because they aren't aiming for good performance anyways).

Well, maybe not quite... of course it's possible that someone would want to deploy a database in a container because of the convenience of assembling all dependencies in a single "package", however, they would never run database on the same node as applications -- that's insanity.

But, even the idea of deploying a database alongside something like kubelet service is cringe... This service is very "fat" and can spike in memory / CPU usage. I would be very strongly opposed to an idea of running a database on the same VM that runs Kubernetes or any container runtime that requires a service to run it.

Obviously, it says nothing about the number of processes that will run on the database node. At the minimum, you'd want to run some stuff for monitoring, that's beside all the system services... but I don't think GP meant "one process" literally. Neither that is realistic nor is it necessary.