CKAD Application Observability and Maintenance Practice Question
You have a pod that is in a 'Pending' state. You run 'kubectl describe pod' and see the event: '0/3 nodes are available: 3 Insufficient cpu'. What is the most likely cause?
⚠ Common exam trap
CNCF often tests the distinction between resource requests (used for scheduling) and resource limits (used for throttling), and candidates mistakenly think 'Insufficient cpu' refers to limits or actual usage rather than the guaranteed request that the scheduler evaluates.
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
✓
The pod's CPU request is larger than the available CPU on any node
The event '0/3 nodes are available: 3 Insufficient cpu' indicates that the Kubernetes scheduler attempted to place the pod on each of the three nodes but found that none had enough allocatable CPU capacity to satisfy the pod's CPU request. This means the sum of CPU requests across all pods on each node, plus the new pod's request, exceeds the node's CPU capacity. The pod remains in 'Pending' because the scheduler cannot find a suitable node until CPU resources are freed or the request is reduced.
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 pod's CPU request is larger than the available CPU on any node
Why this is correct
When a pod's CPU request exceeds the total allocatable CPU capacity on every node in the cluster, the kube-scheduler cannot find a feasible node and leaves the pod in Pending state. The scheduler compares each node's allocatable CPU against the sum of requests for all pods, and a `FailedScheduling` event with `Insufficient cpu` is recorded. This is a scheduling failure, not a runtime failure, so the pod remains Pending until a node with enough free CPU becomes available.
- ✗
The pod requires more memory than any node can provide
Why it's wrong here
If memory were the limiting factor, the scheduler would emit an `Insufficient memory` event, not one mentioning CPU. In the given pod event, the reported resource is specifically CPU, so a memory-based explanation contradicts the observed diagnostic data. Additionally, memory is a different resource dimension, and it is entirely possible that sufficient memory exists on some node even if CPU does not.
- ✗
The pod's liveness probe is failing
Why it's wrong here
The liveness probe is a runtime check that kubelet performs on containers that are already running to decide if they need to be restarted; it does not influence scheduling. A pod in the Pending state has not yet been assigned to a node, so no container is running and no probe has been executed. If a liveness probe fails and becomes critical, the pod will be in CrashLoopBackOff or Running but not Ready, not in Pending.
- ✗
All nodes are tainted and the pod does not tolerate the taints
Why it's wrong here
A taint on a node without a matching toleration in the pod produces a distinct scheduler event, such as `node(s) had taint {key:value}, that the pod didn't tolerate`. That condition also prevents scheduling, but the event text would reference taints, not `Insufficient cpu`. Furthermore, taints are a node-level placement policy, while the reported CPU insufficiency points to a capacity constraint on the node's allocatable resources.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CKAD practice question is part of Courseiva's free CNCF 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 CKAD exam.