twork, region, zone, and subzone.
Traffic will be prioritized to the closest healthy endpoints.
For example, if I have a Service with <code>PreferClose</code> set, with endpoints in zones <code>us-west,us-west,us-east</code>. When
sending traffic from a client in zone <code>us-west</code>, all traffic will go to the two <code>us-west</code> backends.
If one those backends become unhealthy, all traffic will go to the remaining endpoint in <code>us-west</code>.
If that backend becomes unhealthy, traffic will 