A pattern we're seeing a lot of recently is one cluster per "stage" per region, where a "stage" is something like dev/test, canary, and prod. (In some cases only prod is replicated across multiple regions.) I think this may end up being the "sweet spot" for Kubernetes multi-tenancy architecture. The number of clusters isn't quite at the "Kubesprawl" level (I love that phrase and am absolutely going to steal it) -- you can still treat them as pets. But you get good isolation; you can limit access to the prod clusters to only the small set of folks (and perhaps the CD system) authorized to push code there, you can canary Kubernetes upgrades on the canary cluster(s), etc.

As an aside, something that's useful when thinking about Kubernetes multi-tenancy is to understand the distinction between "control plane" multi-tenancy and "data plane" multi-tenancy. Data plane multi-tenancy is about making it safe to share a node (or network) among multiple untrusting users and/or workloads. Examples of existing features for data plane multi-tenancy are gVisor/Kata, PodSecurityPolicy, and NetworkPolicy. Control plane multi-tenancy is about making it safe to share the cluster control plane among multiple untrusting users and/or workloads. Examples of existing features for control plane multi-tenancy are RBAC, ResourceQuota (particularly quota on number of objects; quota on things like cpu and memory are arguably data plane), and the EventRateLimit admission controller.

There's active work in the Kubernetes community in both of these areas; if you'd like to participate (or lurk), please join the kubernetes-wg-multi-tenancy mailing list: http://groups.google.com/forum/#!forum/kubernetes-wg-multite...

Also, I gave a talk at KubeCon EU earlier this year that gives a rough overview of Kubernetes multi-tenancy, that might be of interest to some folks: https://kccnceu18.sched.com/event/Dqvb?iframe=no (links to the slides and YouTube video are near the bottom of the page)

Disclosure: I work at Google on Kubernetes and GKE.