later edit: I'm referring to the fact that when Kubernetes came out it didn't have resource allocation and the answer to "how it compares to Mesos" was that it would run on top of Mesos as a framework.
Kubernetes was not designed with the intention that it would be a Mesos framework. But I think it's very cool that people figured out how to make it work as one!
From pre-1.0, Kubernetes did resource allocation for CPU and memory via its cluster-level scheduler, enforced on the node using the standard container isolation mechanisms provided by Docker.
I'm not David but the answer is yes. After spinning up multiple discrete clusters, you can orchestrate across them by deploying the federation control plane.
What's described in that doc is even easier today thanks to Operators (https://coreos.com/operators), which, to quote the description page, are "application-specific controller[s] that extend[s] the Kubernetes API to create, configure and manage instances of complex stateful applications on behalf of a Kubernetes user."
Disclosure: I work on Kubernetes at Google (and wrote the doc you linked to).
That idea was proposed here:
https://github.com/kubernetes/features/issues/246 ;
there's a pretty thorough design doc linked to from the issue. The decision was made not to add it to the system for now (see the issue for discussion).
> I can't remember which issue this was on, but it seemed like there was some discussion on their GitHub project about making pluggable secrets backends (HashiCorp's Vault was mentioned).
This is not correct. There is a community-owned project that allows Kubernetes to run on Mesos, but it came after standalone Kubernetes.
Disclosure: I work on Kubernetes at Google.