Spot
Instances are Spot VMs (https://cloud.google.com/compute/docs/instances/spot).This option is allowed only for secondary worker (https://cloud.google.com/dataproc/docs/concepts/compute/secondary-vms) groups. Spot VMs are the latest version of preemptible VMs (https://cloud.google.com/compute/docs/instances/preemptible), and provide additional features.