CompTIA Cloud+ (CV0-004)TroubleshootingMedium
A cloud administrator is investigating why an auto-scaling group for a stateless web application is not scaling out during high CPU utilization spikes. The auto-scaling policy is configured to add an instance when average CPU utilization exceeds 70% for 5 minutes. Monitoring shows that average CPU utilization has been consistently above 85% for the past 10 minutes. The auto-scaling group's desired capacity is 2, and the maximum capacity is 5. The current number of running instances is 2. What is the MOST likely reason the auto-scaling group is not scaling out?
- AThe minimum capacity of the auto-scaling group is set too high.
- BThe CPU utilization metric is not being correctly reported to the auto-scaling service.
- CThe auto-scaling group does not have sufficient instance types available in the configured availability zones.
- DThe cooldown period for the auto-scaling group is still active.
Show answer & explanationAnswer & explanation
Correct answer: D. The cooldown period for the auto-scaling group is still active.
Even if the scaling threshold is met, auto-scaling groups typically have a cooldown period after a scaling activity. If a scale-out event recently occurred (or a scale-in) and the cooldown is active, no new scaling activities will be initiated until it expires, preventing further scaling despite high CPU.
Why the other options are wrong
- A. The minimum capacity only prevents scaling *in* below a certain number, and the current instances (2) are at the desired capacity, not the minimum, so this wouldn't prevent scaling out.
- B. The question states 'Monitoring shows that average CPU utilization has been consistently above 85%', implying the metric is being reported correctly.
- C. If instance types were unavailable, the auto-scaling group would typically report a launch failure, not simply fail to scale out silently despite meeting the threshold.
Auto-Scaling Cooldown Period
A configurable setting in an auto-scaling group that prevents additional scaling activities from being triggered immediately after a previous scaling event.
- Allows time for new instances to launch and warm up.
- Prevents rapid, unnecessary scaling actions (flapping).
- Typically lasts several minutes (e.g., 300 seconds/5 minutes).
Memory trick: Cooldown Prevents Quick Scale-Up.