- A
The MIG terminates the 2 least-used VMs to trigger a restart with higher performance settings
Why wrong: Autoscaling never terminates VMs during a traffic spike — it adds instances to handle additional load.
- B
The autoscaler adds VMs until average CPU across the group drops to approximately 60%
The autoscaler computes how many VMs are needed to bring average utilization to the target and scales out accordingly.
- C
The MIG live-migrates instances to larger machine types automatically
Why wrong: Running VMs cannot be automatically resized by the autoscaler — autoscaling adjusts instance count, not machine type.
- D
The MIG restarts all existing VMs to clear cached load
Why wrong: Autoscaling does not restart existing VMs — it adds new instances to distribute incoming load.
Quick Answer
The answer is that the autoscaler adds VMs until the average CPU across the group drops to approximately 60%. This is correct because the MIG autoscaler CPU target utilization acts as a desired threshold; when the average CPU spikes to 90%, the autoscaler calculates the necessary number of instances by dividing the current load by the target (4 VMs × 90% / 60% = 6 VMs) and scales out horizontally to meet that target. On the Google Associate Cloud Engineer exam, this tests your understanding of how autoscalers use target utilization metrics to drive scaling decisions, often appearing in scenario-based questions where a common trap is assuming the autoscaler terminates or restarts VMs during a spike. Remember the key distinction: autoscalers only add or remove instances, never modify existing ones. A helpful memory tip is “spike up, scale out” — when CPU exceeds the target, the autoscaler adds VMs to bring utilization back down to the set percentage.
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. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 (MIG) is running 4 VMs with a CPU autoscaling target of 60%. A traffic spike drives average CPU to 90%. How does the autoscaler respond?
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
The autoscaler adds VMs until average CPU across the group drops to approximately 60%
The autoscaler for a managed instance group (MIG) uses a target utilization metric—here, CPU at 60%. When average CPU exceeds that target (90%), the autoscaler calculates the desired number of VMs to bring utilization back to 60% (e.g., 4 VMs * 90% / 60% = 6 VMs) and adds instances accordingly. It does not terminate, migrate, or restart VMs; it scales out horizontally.
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.
- ✗
The MIG terminates the 2 least-used VMs to trigger a restart with higher performance settings
Why it's wrong here
Autoscaling never terminates VMs during a traffic spike — it adds instances to handle additional load.
- ✓
The autoscaler adds VMs until average CPU across the group drops to approximately 60%
Why this is correct
The autoscaler computes how many VMs are needed to bring average utilization to the target and scales out accordingly.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The MIG live-migrates instances to larger machine types automatically
Why it's wrong here
Running VMs cannot be automatically resized by the autoscaler — autoscaling adjusts instance count, not machine type.
- ✗
The MIG restarts all existing VMs to clear cached load
Why it's wrong here
Autoscaling does not restart existing VMs — it adds new instances to distribute incoming load.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that autoscaling involves modifying existing instances (e.g., restarting, migrating, or resizing) rather than simply adding or removing instances based on a target metric.
Detailed technical explanation
How to think about this question
The autoscaler uses a multiplicative formula: desired VMs = ceil(current VMs * (current utilization / target utilization)). For example, with 4 VMs at 90% CPU and a 60% target, it computes 4 * 90/60 = 6 VMs. The autoscaler also applies a cooldown period (default 60 seconds) before initiating new scaling operations to avoid oscillation. In practice, if the spike is transient, the autoscaler may overshoot and then scale down, but it never modifies existing VM configurations.
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
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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: The autoscaler adds VMs until average CPU across the group drops to approximately 60% — The autoscaler for a managed instance group (MIG) uses a target utilization metric—here, CPU at 60%. When average CPU exceeds that target (90%), the autoscaler calculates the desired number of VMs to bring utilization back to 60% (e.g., 4 VMs * 90% / 60% = 6 VMs) and adds instances accordingly. It does not terminate, migrate, or restart VMs; it scales out horizontally.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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