Google ACE Deploying and Implementing a Cloud Solution Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  Use gcloud compute instances add-metadata to add the startup script to each running instance.

  Why it's wrong here

  Adding metadata directly to a running instance is not a valid way to apply a startup script because startup scripts execute only during the instance boot process. Additionally, MIG-managed instances are considered declaratively managed by the group; any manual changes to them, including metadata, are overwritten if the instance is recreated to match the group's template, and this approach does not propagate the change to the MIG configuration. It also goes against the recommended pattern of using managed instance group updates.

• ✗

  Delete the MIG and recreate it with a new template; you cannot change the template of an existing MIG.

  Why it's wrong here

  Deleting the MIG and recreating it is unnecessary because an existing managed instance group can be updated to use a new instance template without being deleted. You can use the gcloud compute instance-groups managed set-instance-template command or a rolling update to change the template seamlessly. Recreating the entire MIG would cause downtime and require manually reconfiguring autoscaling, health checks, and other settings, violating best practices for managed instance groups.

• ✗

  Edit the existing instance template and add the startup script under 'metadata'.

  Why it's wrong here

  Instance templates are immutable resources in Compute Engine: after creation, you cannot edit or modify any field, including metadata or startup scripts. Even if you could, simply adding a startup script to the template would not affect existing instances in the MIG; it only applies to instances created afterward. Thus, this option fails both due to immutability and because it does not address the current running instances.

• ✓

  Create a new instance template with the startup script, then update the MIG to use the new template via a rolling update.

  Why this is correct

  The correct approach is to create a new instance template that includes the desired startup script in its metadata, then update the MIG to reference this new template using a rolling update. Since instance templates are immutable, creating a new template is mandatory. A rolling update (e.g., gcloud compute instance-groups managed rolling-action start-update) recreates the managed instances incrementally with the new template, ensuring the startup script executes during their boot. This method preserves availability and aligns with the MIG's declarative management model.

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