CKAD Application Observability and Maintenance Practice Question
This CKAD practice question tests your understanding of application observability and maintenance. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
You are a platform engineer at a company that runs a microservices architecture on Kubernetes. The application consists of a frontend service (Node.js), a backend API (Go), and a PostgreSQL database. All components are deployed in the same namespace 'production'. Recently, the backend API has been experiencing intermittent 503 errors from the frontend. The backend API Pods have CPU limits set to 500m and memory limits to 256Mi. The backend API exposes metrics at /metrics and has a liveness probe (HTTP GET /healthz) and a readiness probe (HTTP GET /ready). You notice that during traffic spikes, the backend API Pods are restarted frequently. You examine the metrics and see that memory usage spikes to 250Mi during high load. What is the most likely cause of the restarts and 503 errors?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The memory limit is set too low; the container is being OOMKilled during traffic spikes.
The backend API Pods are being restarted frequently because the memory limit of 256Mi is too close to the observed memory usage of 250Mi during traffic spikes. When memory usage hits the limit, the Linux kernel's OOM killer terminates the container (OOMKilled), causing the Pod to restart. This restart leads to temporary unavailability, which the frontend sees as 503 errors.
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.
✗
The liveness probe is misconfigured and should use a TCP check instead.
Why it's wrong here
The probe type is not the issue; OOM kills cause container restarts.
✓
The memory limit is set too low; the container is being OOMKilled during traffic spikes.
Why this is correct
Memory spikes to 250Mi exceed the 256Mi limit, leading to OOM kills.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The readiness probe is failing because the application is not ready, but the liveness probe keeps it alive.
Why it's wrong here
Readiness failure would cause 503s but not restarts; restarts indicate OOM.
✗
The CPU limit is too low, causing the container to be throttled and timeout.
Why it's wrong here
CPU throttling can cause latency but not container restarts.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse CPU throttling (which causes slowness and timeouts) with OOM kills (which cause restarts), and they may overlook that memory limits are a hard cap enforced by the kernel, while CPU limits are a soft cap enforced by the scheduler.
Detailed technical explanation
How to think about this question
When a container exceeds its memory limit, the cgroup memory controller triggers the OOM killer, which terminates the container's main process. This results in a container exit code of 137 (SIGKILL) and a Pod status of OOMKilled. The kubelet then restarts the container according to the Pod's restartPolicy (default: Always). In contrast, CPU limits are enforced via the Completely Fair Scheduler (CFS) quota, which throttles the container's CPU time but never kills it. The 503 errors from the frontend occur because the backend Pod is unavailable during the restart cycle, and the frontend's retry logic or load balancer may not have a healthy backend to route to.
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
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKAD question in full detail.
Application Observability and Maintenance — This question tests Application Observability and Maintenance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The memory limit is set too low; the container is being OOMKilled during traffic spikes. — The backend API Pods are being restarted frequently because the memory limit of 256Mi is too close to the observed memory usage of 250Mi during traffic spikes. When memory usage hits the limit, the Linux kernel's OOM killer terminates the container (OOMKilled), causing the Pod to restart. This restart leads to temporary unavailability, which the frontend sees as 503 errors.
What should I do if I get this CKAD question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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