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KCNA Kubernetes Fundamentals Practice Question

Which TWO of the following are true about Pod resource limits? (Select TWO)

⚠ Common exam trap

In Kubernetes, the trap here is that candidates often confuse memory limits (hard, enforced by OOM kill) with CPU limits (hard, enforced by throttling), or mistakenly think limits are soft guarantees of allocation rather than caps on consumption.

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

✓

CPU limits are enforced using CFS quotas

Option B is correct because Kubernetes enforces CPU limits via the Linux Completely Fair Scheduler (CFS) quota mechanism, specifically the cpu.cfs_quota_us and cpu.cfs_period_us cgroup settings, which throttle a container's CPU usage once it hits its limit. Option D is correct because Kubernetes validates that a container's limit must be greater than or equal to its request for each resource; otherwise the Pod is rejected, since a limit below the request would be logically inconsistent. Option A is wrong because memory limits are hard limits — the kernel OOM killer terminates the container if it exceeds its memory limit, regardless of free node memory. Option C is wrong because memory limits are not soft; only requests act as soft guarantees, while limits are hard caps enforced by the kernel. Option E is wrong because CPU limits cap maximum usage but do not guarantee CPU allocation; only CPU requests influence scheduling and provide a minimum share under contention.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
A container can use more memory than its limit if the node has free memory
Why it's wrong here
A container exceeding its memory limit is OOM-killed regardless of free node memory; limits are enforced per cgroup, not by node capacity. It tempts because CPU limits allow burst usage when the node is idle, but memory is incompressible and cannot be reclaimed that way.
✓
CPU limits are enforced using CFS quotas
Why this is correct
CPU limits are enforced through CFS quota periods: the kernel throttles a container once it exhausts its allotted CPU time within each 100ms period. This differs from memory limits, which trigger OOM kills rather than throttling, making the statement accurate.
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Memory limits are soft and can be exceeded temporarily
Why it's wrong here
Memory limits are hard: exceeding them triggers OOM termination, not temporary overrun. It tempts because CPU limits are throttled rather than enforced by killing, so people assume memory behaves the same way, but the kernel cgroup OOM killer acts immediately.
✓
Limits must be greater than or equal to requests
Why this is correct
Kubernetes rejects any Pod whose limit is lower than its request, since the scheduler reserves the requested amount while the limit caps burst usage. Setting limits greater than or equal to requests therefore satisfies the API validation constraint, preventing an Invalid specification error at admission time.
✗
Setting CPU limits guarantees that a container will always get that much CPU
Why it's wrong here
CPU limits cap consumption; they do not reserve or guarantee CPU. Guaranteed CPU comes from requests, which the scheduler uses for allocation. It tempts because limits and requests are often configured together, so limits appear to promise capacity, whereas only requests influence scheduling guarantees.

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KCNA Kubernetes Fundamentals Practice Question

Why each option matters

Option-by-option breakdown

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