CKA Troubleshooting Practice Question
A pod is in Pending state. You run 'kubectl describe pod pending-pod' and see an event: '0/3 nodes are available: 3 Insufficient memory'. However, you believe there is enough memory across the cluster. What could be the issue?
⚠ Common exam trap
Test-takers frequently confuse cluster-wide total memory with per-node allocatable memory, assuming that if the sum of free memory across all nodes is sufficient, the pod should schedule — but the scheduler only considers individual node capacity, not aggregated cluster memory.
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 memory request is higher than any node's allocatable memory
The '0/3 nodes are available: 3 Insufficient memory' event indicates that the scheduler could not place the pod because each node lacks enough allocatable memory to satisfy the pod's memory request. Even if the cluster has plenty of total memory, the scheduler evaluates each node individually against the pod's resource requests, not the cluster-wide sum. Therefore, if the pod's memory request exceeds the allocatable memory on every node, the pod will remain Pending.
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 memory request is higher than any node's allocatable memory
Why this is correct
The pod's memory request is higher than any node's allocatable memory. The Kubernetes scheduler performs a feasibility check for each node, comparing the pod's sum of memory requests against the node's allocatable memory (which excludes reserved system resources). If no node can satisfy this request, the scheduler cannot bind the pod, leaving it in Pending state. The `kubectl describe` output would include events such as "0/3 nodes are available: insufficient memory" or "Fit failed" for all nodes, directly indicating that the request exceeds every node's capacity.
- ✗
The cluster is using a resource quota that is exhausted
Why it's wrong here
In Kubernetes, ResourceQuota limits are enforced by an admission controller at pod creation time, not during the scheduling phase. If a resource quota were exhausted, the pod creation would be rejected outright with an error like "exceeded quota" or "forbidden" in the API response, and the pod would never appear as Pending. A pod that is already Pending was successfully admitted, so quota exhaustion cannot be the cause; instead, you would likely see a different event related to scheduling constraints, not a quota-related message.
- ✗
The pod's memory limit is set too low
Why it's wrong here
A pod's memory limit is a cgroup-level constraint that controls the maximum memory a container can use at runtime, not the memory it requests for scheduling. The scheduler only considers memory requests (and other requested resources) when placing pods; limits are irrelevant to node selection. A low memory limit might cause the container to be killed by OOMKiller once running, but it does not prevent the pod from being scheduled. Thus, a memory limit set too low would not leave a pod in Pending state.
- ✗
The nodes have taints that the pod does not tolerate
Why it's wrong here
If nodes have taints that the pod does not tolerate, the scheduler will show explicit taint-related messages in the describe output, such as "0/3 nodes are available: 3 node(s) had untolerated taint" or list the specific taint key. However, this indicates that taints are the sole blocking reason. In this scenario, the actual issue is insufficient memory, which would be reported as an "insufficient memory"/"Fit failed" event; taints are not the causal factor here. Therefore, taints or a lack of tolerations do not explain the described pending state based on the memory-related event.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CKA 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 CKA exam.