- A
Delete all unhealthy instances manually; the MIG will recreate them with the old template
Why wrong: Deleting instances will cause the MIG to recreate them with the new (broken) template, not the old one — this doesn't resolve the issue.
- B
Pause the rolling update, then roll back using `gcloud compute instance-groups managed rolling-action rollback`
Rolling back the MIG update reverts all instances (including the updated ones) to the previous template version, quickly restoring service.
- C
Increase the target size of the MIG to dilute the unhealthy instances
Why wrong: New instances created during a scale-out will use the new (broken) template — this doesn't fix the issue and wastes resources.
- D
Disable autohealing temporarily to prevent the MIG from restarting instances
Why wrong: Disabling autohealing prevents automatic recovery of unhealthy instances — it makes the situation worse, not better.
Quick Answer
The answer is to pause the rolling update and then roll back using `gcloud compute instance-groups managed rolling-action rollback`. This command immediately reverts all instances in the managed instance group to the previous VM template, restoring the known-good configuration that passes health checks. Pausing first stops the rollout from corrupting more instances, while the rollback replaces the unhealthy instances with the old template, allowing the group to stabilize. On the Google Associate Cloud Engineer exam, this scenario tests your understanding of MIG update strategies and the distinction between pausing, stopping, and rolling back—a common trap is attempting to resume or restart the update, which would only continue deploying the faulty template. Remember the key sequence: pause first to halt damage, then rollback to revert. A useful mnemonic is “Pause the pain, rollback the gain”—always stop the spread of failure before restoring the last known good state.
Google ACE Practice Question: Ensuring successful operation of a cloud solution
This ACE practice question tests your understanding of ensuring successful operation of a cloud solution. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A managed instance group serves production traffic. During a rolling update to a new VM template, 30% of instances become unhealthy (failing health checks). The update has not completed yet. What should the team do to immediately restore service?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"immediately / without restart"Why it matters: Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Pause the rolling update, then roll back using `gcloud compute instance-groups managed rolling-action rollback`
Option B is correct because the `gcloud compute instance-groups managed rolling-action rollback` command immediately reverts all instances in the managed instance group (MIG) to the previous template, restoring the known-good configuration. Pausing the update first stops the rollout from continuing to affect more instances, and the rollback command then replaces the unhealthy instances with the old template, allowing health checks to pass again.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Delete all unhealthy instances manually; the MIG will recreate them with the old template
Why it's wrong here
Deleting instances will cause the MIG to recreate them with the new (broken) template, not the old one — this doesn't resolve the issue.
- ✓
Pause the rolling update, then roll back using `gcloud compute instance-groups managed rolling-action rollback`
Why this is correct
Rolling back the MIG update reverts all instances (including the updated ones) to the previous template version, quickly restoring service.
Clue confirmation
The clue word "immediately / without restart" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Increase the target size of the MIG to dilute the unhealthy instances
Why it's wrong here
New instances created during a scale-out will use the new (broken) template — this doesn't fix the issue and wastes resources.
- ✗
Disable autohealing temporarily to prevent the MIG from restarting instances
Why it's wrong here
Disabling autohealing prevents automatic recovery of unhealthy instances — it makes the situation worse, not better.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that manual deletion or disabling autohealing can fix a failed rolling update, when in fact only a deliberate rollback to the previous template restores the known-good state and ensures health checks pass again.
Trap categories for this question
Scenario analysis trap
Disabling autohealing prevents automatic recovery of unhealthy instances — it makes the situation worse, not better.
Detailed technical explanation
How to think about this question
Under the hood, a MIG uses a stateful update process where the `rolling-action rollback` command triggers a `patch` on the instance group's `updatePolicy` to set the `type` to `PROACTIVE` and the `instanceTemplate` to the previous version, then applies the change to all instances. This is distinct from a simple template change because it forces a full re-creation of instances using the old template, bypassing any partial update state. In real-world scenarios, this command is critical when a new template introduces a configuration error (e.g., a misconfigured startup script or a broken application binary) that causes health checks to fail across a significant portion of the group.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this ACE question test?
Ensuring successful operation of a cloud solution — This question tests Ensuring successful operation of a cloud solution — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Pause the rolling update, then roll back using `gcloud compute instance-groups managed rolling-action rollback` — Option B is correct because the `gcloud compute instance-groups managed rolling-action rollback` command immediately reverts all instances in the managed instance group (MIG) to the previous template, restoring the known-good configuration. Pausing the update first stops the rollout from continuing to affect more instances, and the rollback command then replaces the unhealthy instances with the old template, allowing health checks to pass again.
What should I do if I get this ACE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "immediately / without restart". Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 30, 2026
This ACE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the ACE exam.
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