Platform & DevOps·Placement, resources and the pod lifecycle
the expensive GPU nodes sat empty because they push away every workload that has not explicitly said it can live there.
Taint
Also callednode taint, repellent
A mark on a node that repels workloads unless they carry a matching exception. It is the node's own defence — the node decides what it will not take — and it is how you keep general workloads off special hardware, off control-plane machines and off nodes being drained. The direction is the thing to hold on to: a taint pushes away, and only a toleration lets something through.