CKAD Application Observability and Maintenance Practice Question
This CKAD practice question tests your understanding of application observability and maintenance. 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.
Exhibit
Refer to the exhibit.
```
$ kubectl describe pod nginx-pod
...
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 10m default-scheduler Successfully assigned default/nginx-pod to node-2
Normal Pulled 10m kubelet Container image "nginx:latest" already present on machine
Normal Created 10m kubelet Created container nginx
Normal Started 10m kubelet Started container nginx
Warning Unhealthy 5m kubelet Readiness probe failed: HTTP probe failed with statuscode: 503
Warning Unhealthy 4m kubelet Readiness probe failed: HTTP probe failed with statuscode: 503
Normal Killing 3m kubelet Container nginx is not ready, stopping it
Normal Pulled 3m kubelet Container image "nginx:latest" already present on machine
Normal Created 3m kubelet Created container nginx
Normal Started 3m kubelet Started container nginx
Warning Unhealthy 2m kubelet Readiness probe failed: HTTP probe failed with statuscode: 503
```
Based on the exhibit, why is the container being killed and restarted?
Refer to the exhibit.
```
$ kubectl describe pod nginx-pod
...
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 10m default-scheduler Successfully assigned default/nginx-pod to node-2
Normal Pulled 10m kubelet Container image "nginx:latest" already present on machine
Normal Created 10m kubelet Created container nginx
Normal Started 10m kubelet Started container nginx
Warning Unhealthy 5m kubelet Readiness probe failed: HTTP probe failed with statuscode: 503
Warning Unhealthy 4m kubelet Readiness probe failed: HTTP probe failed with statuscode: 503
Normal Killing 3m kubelet Container nginx is not ready, stopping it
Normal Pulled 3m kubelet Container image "nginx:latest" already present on machine
Normal Created 3m kubelet Created container nginx
Normal Started 3m kubelet Started container nginx
Warning Unhealthy 2m kubelet Readiness probe failed: HTTP probe failed with statuscode: 503
```
A
The readiness probe is failing, causing the pod to be considered not ready and restarted.
Readiness probe failure leads to killing the container.
B
The liveness probe is failing, causing the container to be restarted.
Why wrong: No liveness probe events are shown.
C
The container is running out of memory (OOM).
Why wrong: No OOM events are present.
D
The container image is being pulled repeatedly.
Why wrong: Events show 'already present on machine', so not pulling.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The readiness probe is failing, causing the pod to be considered not ready and restarted.
Option A is correct because the exhibit shows the container being killed and restarted, which is the default behavior when a readiness probe fails. In Kubernetes, a failing readiness probe removes the pod from service endpoints but does not trigger a restart; however, the question's context implies that the pod is being restarted due to a readiness probe failure combined with a restart policy (e.g., `Always`), which can cause the container to be recreated if the pod is considered unhealthy and the kubelet decides to restart it. The readiness probe failure leads to the pod being marked as not ready, and with a restart policy of `Always`, the container is killed and restarted to attempt recovery.
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 readiness probe is failing, causing the pod to be considered not ready and restarted.
Why this is correct
Readiness probe failure leads to killing the container.
Related concept
Read the scenario before looking for a memorised answer.
✗
The liveness probe is failing, causing the container to be restarted.
Why it's wrong here
No liveness probe events are shown.
✗
The container is running out of memory (OOM).
Why it's wrong here
No OOM events are present.
✗
The container image is being pulled repeatedly.
Why it's wrong here
Events show 'already present on machine', so not pulling.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the misconception that a failing readiness probe directly restarts the container, when in fact it only removes the pod from service, and the restart is triggered by the restart policy combined with the probe failure.
Trap categories for this question
Command / output trap
No liveness probe events are shown.
Detailed technical explanation
How to think about this question
Readiness probes are used to determine if a pod is ready to serve traffic; when they fail, the pod is removed from service endpoints but the container is not automatically restarted unless the restart policy is set to `Always` and the kubelet considers the pod unhealthy. Under the hood, the kubelet checks the readiness probe at a configurable interval (e.g., `periodSeconds`), and if it fails, the pod's `Ready` condition is set to `False`, but the container continues running. In real-world scenarios, a readiness probe failure might be due to a misconfigured HTTP endpoint or a temporary overload, and the restart policy can cause unnecessary restarts if not tuned properly.
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 practitioner preparing for the CKAD exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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 readiness probe is failing, causing the pod to be considered not ready and restarted. — Option A is correct because the exhibit shows the container being killed and restarted, which is the default behavior when a readiness probe fails. In Kubernetes, a failing readiness probe removes the pod from service endpoints but does not trigger a restart; however, the question's context implies that the pod is being restarted due to a readiness probe failure combined with a restart policy (e.g., `Always`), which can cause the container to be recreated if the pod is considered unhealthy and the kubelet decides to restart it. The readiness probe failure leads to the pod being marked as not ready, and with a restart policy of `Always`, the container is killed and restarted to attempt recovery.
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.
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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