For the first three years of it's existence, the Raspberry Pi Dramble cluster was managed as a set of distinct servers, with a one-to-one relationship between Raspberry Pis and software (e.g. one load balancer, two webservers, two database servers).
In 2018, Jeff Geerling wanted to start learning Kubernetes, so he dug in and converted the Dramble architecture to run on containers managed by Kubernetes.
The work is ongoing—currently all the work is stored in a separate kubernetes branch in the Raspberry Pi Dramble project codebase on GitHub. Please see the README file in the kubernetes branch for more details and instructions for setting up your own Kubernetes cluster using the Dramble.