This is a complicated question to answer.

This isn't my expertise (the cluster orchestration system), but I can answer to the best of my abilities: Titus, today is a system that sits on top of Kubernetes, and uses Kubernetes components to do its thing, but we've substituted many of the systems with our own. For example, closer to my area of knowledge, we've used our own executor / provider along with the Virtual Kubelet project (https://github.com/virtual-kubelet/virtual-kubelet) instead of Kubelet.

We're exploring where we can leverage the Kubernetes ecosystem, adapt components, or help contribute changes back that others can leverage to enable our use of more COTS components of Kubernetes.

tl;dr: We're swapping out the engines while in flight