DOP-C02 Incident and Event Response Practice Question
An application running on Amazon ECS with Fargate is experiencing increased latency. The DevOps team suspects that the task is running out of memory and swapping. Which set of CloudWatch metrics should the team examine to confirm this suspicion?
⚠ Common exam trap
Watch out — candidates often confuse memory metrics with CPU or storage metrics, assuming any resource constraint can cause swapping, but only memory metrics directly indicate memory exhaustion and potential swapping behavior.
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
✓
MemoryUtilized and MemoryReserved
MemoryUtilized and MemoryReserved are the CloudWatch metrics that directly track memory consumption and allocation for ECS tasks using Fargate. When a task runs out of memory, the Linux kernel’s OOM killer may terminate processes, but before that, swapping can occur if swap space is available, causing increased latency. These metrics allow the DevOps team to compare actual memory usage against the task’s memory reservation, confirming if memory pressure is the root cause of the latency.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
NetworkIn and NetworkOut
Why it's wrong here
NetworkIn and NetworkOut quantify bytes transferred over the task's network interfaces, not memory pressure. Swapping is triggered by memory exhaustion within the container, which forces the kernel to write pages to swap space. While heavy network I/O can correlate with increased memory usage indirectly, these metrics provide no visibility into page faults, swap usage, or memory utilization, making them ineffective for diagnosing swapping.
- ✓
MemoryUtilized and MemoryReserved
Why this is correct
MemoryUtilized and MemoryReserved are the correct CloudWatch ECS metrics for Fargate tasks, as they directly measure the task's memory consumption against the memory limit configured in the task definition. When MemoryUtilized consistently approaches or equals MemoryReserved, the container runtime may start swapping memory pages to disk, which degrades performance. Monitoring these two metrics together provides the earliest signal of memory pressure that leads to swapping.
- ✗
CPUUtilization and CPUReservation
Why it's wrong here
CPUUtilization and CPUReservation measure compute resource usage, not memory allocation or consumption. Swapping is a memory-management event where pages are moved between physical memory and disk; it is initiated by memory pressure, not CPU load. Although sustained high CPU can result from swapping due to increased kernel overhead, these metrics do not reveal memory exhaustion and therefore cannot directly indicate whether swapping is occurring.
- ✗
EphemeralStorageUtilized and EphemeralStorageReserved
Why it's wrong here
EphemeralStorageUtilized and EphemeralStorageReserved are not emitted as default CloudWatch metrics for Fargate tasks, so they cannot be used without a custom monitoring solution. Ephemeral storage is the temporary disk space for the container, separate from memory; swapping involves memory pages being written to a swap file, possibly on this storage, but the metrics themselves only track disk usage, not memory or swap activity. Consequently, they are neither available by default nor relevant for diagnosing swapping.
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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.