A locality defines the geographic location of a workload instance.
Represents a large geographic area, such as us-east1. A region typically contains a number of availability zones. A workload's region is determined by the value of the “topology.kubernetes.io/region” label (or the deprecated “failure-domain.beta.kubernetes.io/region” one) of the Node that is running it.
Represents an availability zone within a region, e.g. us-east-1a. A workload's zone is determined by the value of the “topology.kubernetes.io/zone” label (or the deprecated “failure-domain.beta.kubernetes.io/zone” one) of the Node that is running it.
A zone can be divided into sub-zones to have even more fine-grained control over load balancing behavior. The sub-zone concept doesn't exist in Kubernetes. This value is derived by the Istio-specific “topology.istio.io/subzone” Node label.