This CKA practice question tests your understanding of troubleshooting. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 are a CKA managing a production cluster with 5 worker nodes. A developer reports that a new deployment 'payment-service' is not accessible from other pods via its Service 'payment-svc' in the 'default' namespace. The Service is of type ClusterIP with selector 'app: payment'. The deployment has 3 replicas, all showing 'Running' status. From a test pod, you run 'curl http://payment-svc:8080' and get 'Connection refused'. You verify that the pods are listening on port 8080 and the container's readiness probe passes. 'kubectl get endpoints payment-svc' shows no endpoints. 'kubectl describe svc payment-svc' shows the selector 'app=payment'. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The pods have label 'app: payment-service' instead of 'app: payment', so the service selector does not match.
The most likely cause is that the pods' labels do not match the Service's selector. The Service 'payment-svc' uses selector 'app: payment', but the pods have label 'app: payment-service'. Since the selector does not match any pods, the Service's endpoints list is empty, causing 'Connection refused' when trying to reach the ClusterIP. The pods are running and listening on port 8080, but the Service has no backends to forward traffic to.
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.
✗
A NetworkPolicy is blocking traffic from the test pod to the service IP.
Why it's wrong here
NetworkPolicy would not affect endpoint population.
✗
The service type should be NodePort to allow in-cluster access.
Why it's wrong here
ClusterIP is sufficient for in-cluster access.
✗
The readiness probe is failing on all pods, causing them to be removed from service endpoints.
Why it's wrong here
Readiness failure would show endpoints but with 'not ready' status, not empty.
✓
The pods have label 'app: payment-service' instead of 'app: payment', so the service selector does not match.
Why this is correct
Selector mismatch is the classic cause of empty endpoints.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a NetworkPolicy or readiness probe issue when they see 'Connection refused', but the empty endpoints list directly points to a selector mismatch, which is a fundamental Kubernetes networking concept tested in the CKA.
Trap categories for this question
Command / output trap
Readiness failure would show endpoints but with 'not ready' status, not empty.
Detailed technical explanation
How to think about this question
Kubernetes Services use label selectors to dynamically discover pods and populate endpoints. The endpoint controller watches for pods matching the selector and updates the Endpoints object accordingly. If the selector does not match any pod labels, the endpoints list remains empty, and any traffic to the Service's ClusterIP will be rejected with 'Connection refused' because there are no backends to forward to. This is a common misconfiguration when labels are not consistently applied across deployments and services.
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 practitioner preparing for the CKA exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKA question in full detail.
Troubleshooting — This question tests Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The pods have label 'app: payment-service' instead of 'app: payment', so the service selector does not match. — The most likely cause is that the pods' labels do not match the Service's selector. The Service 'payment-svc' uses selector 'app: payment', but the pods have label 'app: payment-service'. Since the selector does not match any pods, the Service's endpoints list is empty, causing 'Connection refused' when trying to reach the ClusterIP. The pods are running and listening on port 8080, but the Service has no backends to forward traffic to.
What should I do if I get this CKA question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.