The answer is that the container is OOMKilled because its memory allocation of 600Mi exceeds the configured memory limit of 512Mi. Kubernetes enforces memory limits through the cgroup memory controller; when a container attempts to allocate more memory than its limit, the kernel’s Out-Of-Memory (OOM) killer terminates the container process, resulting in an OOMKilled status. On the Certified Kubernetes Application Developer CKAD exam, this scenario tests your understanding of how resource limits are strictly enforced—unlike CPU limits, which can be throttled, memory limits are hard caps. A common trap is assuming the pod itself is killed, but only the offending container is terminated, and the pod may restart depending on its restart policy. Remember the mnemonic: “Memory is a hard wall, CPU is a soft throttle.”
CKAD Practice Question: Application Environment, Configuration and Security
This CKAD practice question tests your understanding of application environment, configuration and security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 deploy a pod with resource requests: cpu: 500m, memory: 256Mi and limits: cpu: 1, memory: 512Mi. The container tries to allocate 600Mi of memory. What happens?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The container is OOMKilled because it exceeds the memory limit
The correct answer is A because the container's memory allocation of 600Mi exceeds its configured memory limit of 512Mi. Kubernetes enforces memory limits using the cgroup memory controller; when a container attempts to allocate more memory than its limit, the kernel's Out-Of-Memory (OOM) killer terminates the container process. This results in the container being OOMKilled, as recorded in the pod status.
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 container is OOMKilled because it exceeds the memory limit
Why this is correct
Exceeding the memory limit triggers OOM kill.
Related concept
Read the scenario before looking for a memorised answer.
✗
The container runs normally, but memory usage is throttled
Why it's wrong here
Memory cannot be throttled like CPU; exceeding limits leads to OOM kill.
✗
The container runs normally because requests are the only constraints
Why it's wrong here
Limits are also constraints; they are enforced.
✗
The container is evicted from the node
Why it's wrong here
Eviction occurs when node resources are low, not directly due to a container exceeding its limit.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the misconception that memory, like CPU, can be throttled when limits are exceeded, but memory is a non-compressible resource and exceeding its limit always results in an OOM kill, not throttling.
Detailed technical explanation
How to think about this question
Under the hood, Kubernetes sets cgroup memory limits via the `memory.limit_in_bytes` file in the container's cgroup. When the container's memory usage hits this limit, the kernel invokes the OOM killer, which selects a process based on an oom_score and sends a SIGKILL. In a real-world scenario, a Java application with a heap size set via `-Xmx` that exceeds the container's memory limit will be OOMKilled, causing downtime unless the pod is part of a Deployment with a restart policy.
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 Environment, Configuration and Security — This question tests Application Environment, Configuration and Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The container is OOMKilled because it exceeds the memory limit — The correct answer is A because the container's memory allocation of 600Mi exceeds its configured memory limit of 512Mi. Kubernetes enforces memory limits using the cgroup memory controller; when a container attempts to allocate more memory than its limit, the kernel's Out-Of-Memory (OOM) killer terminates the container process. This results in the container being OOMKilled, as recorded in the pod status.
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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