DOP-C02 Incident and Event Response Practice Question
A company runs a microservices application on Amazon ECS with Fargate. The application includes a service that processes messages from an Amazon SQS queue. Recently, the processing time has increased, and the SQS queue depth is growing. The CloudWatch metrics show that the ECS service's CPU utilization is consistently around 70%, memory utilization is 80%, and the number of running tasks is at the maximum allowed (10). The service is configured with a target tracking scaling policy based on CPU utilization with a target value of 50%. However, the auto scaling does not seem to be adding tasks. The engineer checks the ECS service events and finds no scaling activity. What is the MOST likely reason the auto scaling is not working, and what action should be taken to resolve the issue?
⚠ Common exam trap
Watch out — candidates often assume the scaling policy itself is misconfigured or that Fargate lacks support for target tracking, when in reality the issue is the hard cap on the maximum number of tasks preventing any scale-out action.
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 service has reached the maximum number of tasks defined in the auto scaling configuration; increase the maximum tasks.
The auto scaling is not adding tasks because the ECS service has already reached the maximum number of tasks defined in the auto scaling configuration (10). With CPU utilization at 70% and the target tracking policy set to 50%, the policy would normally trigger scale-out actions, but since the maximum task count is already hit, no scaling activity occurs. The engineer must increase the maximum tasks in the auto scaling configuration to allow further scale-out.
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 service has reached the maximum number of tasks defined in the auto scaling configuration; increase the maximum tasks.
Why this is correct
The ECS service's Application Auto Scaling target tracking policy is capped by a maximum capacity of 10 tasks. Since the service is already running at that desired count of 10, the policy cannot scale out any further even though the CloudWatch metric is above the target value. To resolve the issue, increase the maximum tasks (for example, from 10 to 15) in the scaling configuration, which allows the policy to add more task instances.
- ✗
The scaling policy is not properly configured; recreate it with a lower target value.
Why it's wrong here
The scaling policy itself is functioning as intended because the metric is above the target and the policy is actively trying to scale out. Recreating it with a lower target value would only increase the desired count further, but the hard cap of 10 tasks prevents any change from taking effect. The root cause is the maximum capacity limit, not the policy's target setpoint.
- ✗
The CloudWatch metric is not being emitted correctly; check the metric namespace.
Why it's wrong here
The CloudWatch metric is being emitted correctly because it is visible and showing the expected pattern of high CPU utilization that exceeds the target value. The namespace (for example, ECS/ContainerInsights or a custom namespace) is correctly configured since the metric is present. This eliminates a missing-metric problem; the scaling failure stems from the task capacity limit, not from metric emission.
- ✗
The ECS service is using Fargate, which does not support target tracking scaling policies.
Why it's wrong here
Amazon ECS on Fargate fully supports target tracking scaling policies through Application Auto Scaling, with no limitation preventing their use. Fargate services can use the same scaling policies as EC2 launch type, including target tracking for CPU, memory, and other custom metrics. Therefore the Fargate launch type is not a barrier to scaling; the capacity cap is what is blocking the scale-out.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.