we scale up to about 100 machines. We use spot instances EXTENSIVELY. And that configuration was tricky actually. Its been a couple of months now. Works pretty ok.

k3s is actually pretty simple to use now. the tricky part was to integrate with https://github.com/kubernetes/cloud-provider-aws and https://github.com/DirectXMan12/k8s-prometheus-adapter

The hardest part is to get it to work with spot instances. we use https://github.com/AutoSpotting/AutoSpotting to integrate with it.