What should you do?

You have developed a non-critical update to your application that is running in a managed instance group, and have created a new instance template with the update that you want to release. To prevent any possible impact to the application, you don’t want to update any running instances. You want any new instances that are created by the managed instance group to contain the new update .

What should you do?
A . Start a new rolling restart operation.
B . Start a new rolling replace operation.
C . Start a new rolling update. Select the Proactive update mode.
D . Start a new rolling update. Select the Opportunistic update mode.

Answer: D

Explanation:

In certain scenarios, an opportunistic update is useful because you don’t want to cause instability to the system if it can be avoided. For example, if you have a non-critical update that can be applied as necessary without any urgency and you have a MIG that is actively being autoscaled, perform an opportunistic update so that Compute Engine does not actively tear down your existing instances to apply the update. When resizing down, the autoscaler preferentially terminates instances with the old template as well as instances that are not yet in a RUNNING state.