CKA Troubleshooting Practice Question
You have a Deployment with 3 replicas. One of the pods is in 'Pending' state. 'kubectl describe pod' shows: 'Warning FailedScheduling 0/4 nodes are available: 1 node(s) had taint {key1: value1}, that the pod didn't tolerate, 3 node(s) didn't match pod anti-affinity rules.' Which two issues are preventing the pod from being scheduled?
⚠ Common exam trap
The CKA exam often tests the ability to read the exact error message from `kubectl describe pod` and map each clause to a specific scheduling issue, rather than assuming generic problems like resource limits or node selectors.
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
✓
Taint toleration mismatch and pod anti-affinity conflicts
The error message explicitly states two distinct scheduling failures: '1 node(s) had taint {key1: value1}, that the pod didn't tolerate' and '3 node(s) didn't match pod anti-affinity rules.' These correspond directly to a taint toleration mismatch and pod anti-affinity conflicts. No other issues (node selector, resource constraints) are mentioned in the describe output.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Taint toleration mismatch and pod anti-affinity conflicts
Why this is correct
The event log explicitly reports a taint toleration mismatch, meaning the node carries taints the pod does not tolerate, and simultaneously reports a pod anti-affinity conflict, meaning the pod's scheduling constraints prevent it from co-locating with pods that match its anti-affinity selector. Both of these conditions together are present in the pod's unschedulable event. This answer correctly identifies the two distinct scheduling constraints that block the pod, so it is the right choice.
- ✗
Pod anti-affinity and node selector issues
Why it's wrong here
Although pod anti-affinity is indeed part of the scheduling failure, the notion of a node selector issue is unsupported: the event description and deployment spec do not mention any nodeSelector or nodeAffinity term. A node selector problem would surface as an inability to find a node whose labels match the selector, typically producing a different event message than the taint and anti-affinity lines seen here. Because it introduces an unverified constraint and omits the confirmed taint-toleration mismatch, this answer is incorrect.
- ✗
Node selector and taint toleration mismatch
Why it's wrong here
This answer correctly recognizes the taint toleration mismatch as one of the blocking factors, but it incorrectly substitutes a node selector issue for the pod anti-affinity conflict that the event explicitly describes. No node selector or node affinity rule is present in the deployment, so there is no evidence for that claim. Additionally, by ignoring the anti-affinity constraint, it fails to account for a central reason the pod cannot be placed, making the answer wrong despite its partially correct taint diagnosis.
- ✗
Resource constraints and taint toleration mismatch
Why it's wrong here
Resource constraints are not mentioned in the event or manifest; an actual resource shortfall would appear as 'Insufficient cpu' or 'Insufficient memory' in the pod conditions and events, not as a taint/toleration message. The event specifically calls out taint toleration mismatch and pod anti-affinity conflict, not resource pressure on the node. Pairing taint mismatch with an unsupported resource-constraint explanation ignores the confirmed anti-affinity condition, so this answer is incorrect.
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JA
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.