DOP-C02 Monitoring and Logging Practice Question
A company has deployed a containerized application on Amazon ECS with Fargate. The application is fronted by an Application Load Balancer (ALB). The DevOps team is using CloudWatch Container Insights to monitor the ECS cluster. They notice that the 'MemoryUtilized' metric for the service is consistently above 80%, and the 'CPUUtilized' is around 50%. The ALB's 'TargetResponseTime' is increasing over time. The team wants to resolve the performance issue. Which action should the team take?
⚠ Common exam trap
DOP-C02 often tests whether candidates can diagnose the bottleneck from metrics — the trap is picking CPU scaling or horizontal scaling when the data clearly shows memory pressure as the root cause of rising response time.
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
✓
Increase the memory limit for the ECS task definition to allow the container to use more memory.
The metrics show MemoryUtilized consistently above 80% while CPUUtilized is only around 50%, and TargetResponseTime is rising — this is a classic memory-bound bottleneck. When a container approaches its memory limit, the kernel may reclaim page cache, trigger GC pressure, or begin swapping (if enabled), all of which degrade response time. Increasing the memory limit in the task definition gives the container headroom to operate without memory pressure, directly addressing the root cause.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Increase the memory limit for the ECS task definition to allow the container to use more memory.
Why this is correct
The ECS task definition's memory limit is a hard limit enforced by Docker; when the container's memory utilization consistently exceeds 80%, it is likely approaching or hitting that ceiling, leading to OOM kills or severe performance degradation. Increasing the memory limit lets the container allocate more heap or working set, directly relieving the memory bottleneck. This is a vertical scaling action, and you must also ensure the EC2 instance has enough free memory to support the increased limit.
- ✗
Increase the CPU limit for the ECS task definition to improve performance.
Why it's wrong here
While increasing the CPU limit in the ECS task definition would give the container more CPU shares, the observed CPU utilization is only 50%, meaning the CPU is not the constraining resource. Memory pressure and CPU saturation are independent; allocating more CPU does not reduce the amount of memory the application consumes. Moreover, over-provisioning CPU can lead to wasted compute capacity, higher cost, and potentially introduce resource contention on the underlying instance without addressing the OOM risk.
- ✗
Increase the number of ALB targets by adding more availability zones.
Why it's wrong here
The ALB target group routes traffic to ECS tasks, but adding more availability zones does not change the memory limit or memory pressure of the already-running containers. Increasing the number of AZs primarily improves fault tolerance and increases the pool of potential target IPs for the ALB; it does not alter the per-task memory configuration or the container's memory usage. Since the issue is a memory bottleneck inside the container, ALB-level changes will have no effect on the root cause.
- ✗
Increase the desired count of the ECS service to distribute the load across more tasks.
Why it's wrong here
Increasing the desired count of the ECS service performs horizontal scaling, which can distribute incoming requests across more container instances and temporarily reduce per-task memory pressure. However, the root cause is the memory limit defined in the task definition; if each new task has the same low limit, they will still hit the same OOM threshold when they receive their share of traffic. Horizontal scaling also increases cost and operational complexity without resolving the underlying configuration deficiency, making it an indirect and often incomplete remedy compared to raising the memory limit.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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.