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Question 689 of 1,740

Incident and Event Response →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is to create a CloudWatch alarm on CPU utilization that performs an EC2 action to stop the instance, and configure the Auto Scaling group with a target tracking scaling policy based on CPU utilization. This solution directly addresses the root cause—high CPU utilization causing the health check endpoint to time out after 5 seconds—by forcibly stopping the overloaded instance, which removes it from the ALB target group and stops traffic routing. The target tracking policy then automatically scales out new instances to handle the increased load, ensuring capacity matches demand without manual intervention. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how to integrate CloudWatch alarms with EC2 instance actions to remediate health check failures, a common trap being to rely solely on Auto Scaling health checks, which only replace instances after they are marked unhealthy by the load balancer. Memory tip: “Stop the CPU hog, then scale the log”—the alarm stops the bad instance, and the scaling policy adds good ones.

DOP-C02 Incident and Event Response Practice Question

This DOP-C02 practice question tests your understanding of incident and event response. 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 company runs a critical web application on AWS. The application is deployed across multiple Availability Zones using an Application Load Balancer (ALB) with an Auto Scaling group of EC2 instances. The Auto Scaling group uses a launch template that specifies an Amazon Linux 2 AMI. The application stores session state in an ElastiCache Redis cluster. Recently, the operations team received alerts that the application is returning 503 errors intermittently. Investigation shows that the ALB target group health checks are failing for some instances, but those instances are still in service. The CloudWatch logs from the instances show that the application is running, but the health check endpoint is timing out after 5 seconds. The health check is configured with a 5-second timeout, 10-second interval, and 2 consecutive successes required to mark healthy. The DevOps engineer suspects that the issue is due to high CPU utilization on the instances causing the health check to respond slowly. The engineer wants to implement a solution that prevents the ALB from routing traffic to instances that are experiencing high CPU, and also automatically scales out to handle the increased load. What should the engineer do?

Question 1hardmultiple choice

Review the full routing breakdown →

A
Configure the Auto Scaling group to use ELB health checks and set the health check grace period to 600 seconds.
Why wrong: This delays health checks but does not prevent high CPU instances from being used.
B
Create a CloudWatch alarm on CPU utilization and use it to perform an EC2 action to stop the instance, and configure the Auto Scaling group to use a target tracking scaling policy based on CPU utilization.
Stopping high CPU instances removes them from the ALB, and target tracking scaling adds capacity when needed.
C
Create a scheduled scaling action to add more instances during peak hours.
Why wrong: Scheduled scaling does not respond to real-time CPU spikes.
D
Increase the health check timeout to 10 seconds and the interval to 20 seconds to give instances more time to respond.
Why wrong: This would allow slow instances to remain in service longer, potentially worsening the issue.

Full breakdown with real-world context →

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

✓

Create a CloudWatch alarm on CPU utilization and use it to perform an EC2 action to stop the instance, and configure the Auto Scaling group to use a target tracking scaling policy based on CPU utilization.

Option B is correct because it addresses both the immediate issue (high CPU causing health check timeouts) and the scaling requirement. Stopping the instance via a CloudWatch alarm removes it from the ALB target group, preventing traffic routing to unhealthy instances. The target tracking scaling policy based on CPU utilization automatically adds instances when CPU is high, ensuring capacity matches demand.

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.

✗
Configure the Auto Scaling group to use ELB health checks and set the health check grace period to 600 seconds.
Why it's wrong here
This delays health checks but does not prevent high CPU instances from being used.
✓
Create a CloudWatch alarm on CPU utilization and use it to perform an EC2 action to stop the instance, and configure the Auto Scaling group to use a target tracking scaling policy based on CPU utilization.
Why this is correct
Stopping high CPU instances removes them from the ALB, and target tracking scaling adds capacity when needed.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create a scheduled scaling action to add more instances during peak hours.
Why it's wrong here
Scheduled scaling does not respond to real-time CPU spikes.
✗
Increase the health check timeout to 10 seconds and the interval to 20 seconds to give instances more time to respond.
Why it's wrong here
This would allow slow instances to remain in service longer, potentially worsening the issue.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates may think increasing health check timeout or grace period solves the problem, but AWS expects you to recognize that high CPU instances should be removed from service and replaced via scaling, not just given more time to respond.

Detailed technical explanation

How to think about this question

When an EC2 instance is stopped via a CloudWatch alarm, the Auto Scaling group automatically terminates it and launches a replacement, which effectively removes the instance from the ALB target group. Target tracking scaling policies use a predefined metric (e.g., CPUUtilization) to dynamically adjust the desired capacity, maintaining the target value (e.g., 50%) by adding or removing instances. This approach ensures that instances with high CPU are replaced and overall capacity scales with demand, unlike passive health check adjustments.

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.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this DOP-C02 question test?

Incident and Event Response — This question tests Incident and Event Response — 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 and use it to perform an EC2 action to stop the instance, and configure the Auto Scaling group to use a target tracking scaling policy based on CPU utilization. — Option B is correct because it addresses both the immediate issue (high CPU causing health check timeouts) and the scaling requirement. Stopping the instance via a CloudWatch alarm removes it from the ALB target group, preventing traffic routing to unhealthy instances. The target tracking scaling policy based on CPU utilization automatically adds instances when CPU is high, ensuring capacity matches demand.

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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Same concept, more angles

1 more ways this is tested on DOP-C02

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. Which TWO actions should be taken to ensure a highly available and resilient architecture for a critical web application on AWS? (Choose two.)

easy

A.Enable Amazon CloudFront with multiple origins.
✓ B.Use an Auto Scaling group to maintain a desired number of instances.
C.Use a Multi-AZ RDS deployment with read replicas.
D.Store backups in a different AWS Region.
✓ E.Deploy the application across multiple Availability Zones.

Why B: Correct: A and D. Deploying across multiple Availability Zones provides resilience against AZ failures. Using an Auto Scaling group ensures capacity is maintained. Option B provides read scalability but not write availability. Option C is for disaster recovery, not immediate availability. Option E is for performance, not availability.

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This DOP-C02 practice question is part of Courseiva's free Amazon Web Services 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 DOP-C02 exam.