The answer is to create a CloudWatch alarm on CPU utilization that triggers an Auto Scaling policy to replace the instance. This solution is correct because it directly links the performance metric—high CPU—to an automated lifecycle action, where the alarm state initiates a scaling policy that terminates the unhealthy EC2 instance and launches a replacement, effectively implementing automatic instance replacement based on CPU metric. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of integrating CloudWatch alarms with Auto Scaling lifecycle hooks or simple scaling policies, rather than relying on manual intervention or separate services like Lambda for instance health checks. A common trap is confusing instance replacement with instance recovery; remember that recovery restarts the same instance on new hardware, while replacement terminates and launches a new one. Memory tip: "Alarm triggers action, not just notification"—the key is that the alarm must directly drive the scaling policy, not merely alert.
DOP-C02 Resilient Cloud Solutions Practice Question
This DOP-C02 practice question tests your understanding of resilient cloud solutions. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 company experiences intermittent high latency for a web application running on EC2 behind an ALB. They want to monitor and automatically replace instances that have high CPU. Which solution meets this requirement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a CloudWatch alarm on CPU utilization that triggers an Auto Scaling policy to replace the instance
Option A is correct because you can configure a CloudWatch alarm on the EC2 instance's CPU utilization metric, and then use that alarm to trigger an Auto Scaling lifecycle hook or a scaling policy that terminates the unhealthy instance and launches a replacement. This directly ties performance monitoring to automated instance replacement, meeting the requirement to replace instances with high CPU.
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.
✓
Create a CloudWatch alarm on CPU utilization that triggers an Auto Scaling policy to replace the instance
Why this is correct
CloudWatch alarm can trigger a scale-in or terminate action.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use Auto Scaling scheduled scaling actions to replace instances at peak times
Why it's wrong here
Scheduled actions do not react to real-time CPU.
✗
Use AWS Lambda to periodically check CPU and terminate high-CPU instances
Why it's wrong here
Lambda cannot directly launch new instances without Auto Scaling.
✗
Configure the ALB health check to mark instances unhealthy when CPU is high
Why it's wrong here
ALB health checks do not measure CPU.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse ALB health checks with instance health monitoring, assuming ALB can react to CPU metrics, when in fact ALB health checks only verify application-level responsiveness (e.g., HTTP status codes) and cannot directly measure CPU utilization.
Detailed technical explanation
How to think about this question
Under the hood, the CloudWatch alarm triggers an Auto Scaling lifecycle hook that puts the instance in a 'terminating:wait' state, allowing for custom actions before termination, or directly invokes a scaling policy to decrement the desired count and launch a new instance. The key subtlety is that the alarm must be based on the average CPU utilization over a period (e.g., 5 minutes) to avoid flapping, and the Auto Scaling group must have a minimum size of at least 1 to ensure replacement. In a real-world scenario, this approach is commonly used with a step scaling policy to gradually replace instances only when CPU exceeds a threshold, preventing unnecessary churn from brief spikes.
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
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Resilient Cloud Solutions — This question tests Resilient Cloud Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a CloudWatch alarm on CPU utilization that triggers an Auto Scaling policy to replace the instance — Option A is correct because you can configure a CloudWatch alarm on the EC2 instance's CPU utilization metric, and then use that alarm to trigger an Auto Scaling lifecycle hook or a scaling policy that terminates the unhealthy instance and launches a replacement. This directly ties performance monitoring to automated instance replacement, meeting the requirement to replace instances with high CPU.
What should I do if I get this DOP-C02 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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Question Discussion
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