- A
Use AWS Auto Scaling to scale the ECS service based on the custom metric.
Why wrong: AWS Auto Scaling is not directly used for ECS Service Auto Scaling; Application Auto Scaling is used.
- B
Create a CloudWatch dashboard to visualize the metric and manually adjust the service count.
Why wrong: Manual intervention is not automated scaling.
- C
Publish the custom metric to Amazon CloudWatch, then create a target tracking scaling policy in Application Auto Scaling for the ECS service.
This is the recommended approach for scaling ECS services using custom metrics.
- D
Use an AWS Lambda function to directly update the desired count of the ECS service based on the metric.
Why wrong: Lambda can be used but it is not a best practice; CloudWatch and Application Auto Scaling provide a native solution.
Quick Answer
The answer is to publish the custom metric to Amazon CloudWatch, then create a target tracking scaling policy in Application Auto Scaling for the ECS service. This is correct because Application Auto Scaling can consume any CloudWatch custom metric to dynamically adjust the desired count of an ECS service, even with AWS Fargate, by maintaining a target value for the metric—such as active user sessions—without needing manual intervention. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how custom metrics for ECS auto scaling integrate with CloudWatch and Application Auto Scaling, often appearing as a trap where candidates mistakenly choose Lambda or direct scaling options. A common pitfall is assuming Lambda can directly scale ECS services, but it cannot; only Application Auto Scaling policies can. Memory tip: think “Publish, then Target” — publish the custom metric to CloudWatch, then set a target tracking policy in Application Auto Scaling.
DOP-C02 Monitoring and Logging Practice Question
This DOP-C02 practice question tests your understanding of monitoring and logging. 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 is running a production application on Amazon ECS with AWS Fargate. The application has unpredictable traffic patterns and occasionally experiences increased latency. The DevOps team needs to configure scaling based on a custom metric that tracks the number of active user sessions in real time. Which solution will allow the team to scale the ECS service based on this custom metric?
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
Publish the custom metric to Amazon CloudWatch, then create a target tracking scaling policy in Application Auto Scaling for the ECS service.
Option B is correct because CloudWatch custom metrics can be used with ECS Service Auto Scaling. Option A is wrong because Application Auto Scaling is the correct service, but it is not direct. Option C is wrong because Lambda cannot directly scale ECS services. Option D is wrong because CloudWatch dashboards are for visualization only.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use AWS Auto Scaling to scale the ECS service based on the custom metric.
Why it's wrong here
AWS Auto Scaling is not directly used for ECS Service Auto Scaling; Application Auto Scaling is used.
- ✗
Create a CloudWatch dashboard to visualize the metric and manually adjust the service count.
Why it's wrong here
Manual intervention is not automated scaling.
- ✓
Publish the custom metric to Amazon CloudWatch, then create a target tracking scaling policy in Application Auto Scaling for the ECS service.
Why this is correct
This is the recommended approach for scaling ECS services using custom metrics.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
Use an AWS Lambda function to directly update the desired count of the ECS service based on the metric.
Why it's wrong here
Lambda can be used but it is not a best practice; CloudWatch and Application Auto Scaling provide a native solution.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.
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Monitoring and Logging — study guide chapter
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
Monitoring and Logging — This question tests Monitoring and Logging — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Publish the custom metric to Amazon CloudWatch, then create a target tracking scaling policy in Application Auto Scaling for the ECS service. — Option B is correct because CloudWatch custom metrics can be used with ECS Service Auto Scaling. Option A is wrong because Application Auto Scaling is the correct service, but it is not direct. Option C is wrong because Lambda cannot directly scale ECS services. Option D is wrong because CloudWatch dashboards are for visualization only.
What should I do if I get this DOP-C02 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
About these practice questions
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Last reviewed: Jun 20, 2026
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.
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