There should be individual ASGs for each AZ that has been specified during the cluster creation. Currently, we just create one ASG for workers and one for the masters.

For eg. Consider the cluster has been created by specifying two AZs

"availability_zones": [
"eu-west-1a",
"eu-west-1b",]

We should have 4 ASGs for master and worker nodes in each AZ( two each). This is needed for the following scenario -
We have a PMK AWS cluster for KF with autoscaling enabled. During the cluster upgrade, one of the worker nodes failed to drain as it had pods running on it with EBS volumes attached as PVs and there was no other worker node present in the same AZ. This worker node may have been created during autoscaling in a different AZ altogether.

Also, there are advantages to having masters in different ASGs as well