You must deploy a new version to a managed instance group while minimizing cost and keeping instance count constant; only proceed when each new instance is healthy. Which rolling action parameters achieve this?

The correct answer is rolling-action with maxSurge: 0 and maxUnavailable: 1. This configuration ensures that the instance count remains constant (maxSurge: 0 prevents new instances from being created beyond the target size), and the update proceeds by taking one instance offline at a time (maxUnavailable: 1). The update only progresses when the replacement instance is healthy, fulfilling the requirement to only proceed when each new instance is healthy. The other options are incorrect because: maxSurge: 1 and maxUnavailable: 0 would temporarily increase the instance count, violating the "constant instance count" requirement. maxHealthy and maxUnhealthy are not standard parameters for controlling rolling updates in Google Cloud managed instance groups. The correct parameters are maxSurge and maxUnavailable.