This CKAD practice question tests your understanding of services and networking. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
An Ingress resource routes traffic to a Service 'web' on port 80. The Service has multiple endpoints but all return 503. What should be checked first?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check the readiness probe of the Pods
A 503 Service Unavailable error from the Ingress indicates the upstream Service is not ready to serve traffic. The most common cause is Pods failing their readiness probes, which removes them from the Service's endpoint list. Checking the readiness probe status directly addresses why the Service has endpoints but returns 503.
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.
✗
Ensure that the Service type is ClusterIP
Why it's wrong here
Ingress works with ClusterIP, but type is not the cause of 503.
✓
Check the readiness probe of the Pods
Why this is correct
503 often indicates Pods are not ready; readiness probe failing causes removal from endpoints.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Verify that the Service port matches the Pod's container port
Why it's wrong here
If mismatch, endpoints wouldn't be populated; they are, so port likely matches.
✗
Check the Ingress controller logs
Why it's wrong here
Ingress controller logs would show routing info, not application health.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the distinction between readiness and liveness probes, where candidates mistakenly check liveness or assume a port mismatch, but readiness directly controls traffic routing via Services.
Trap categories for this question
Command / output trap
Ingress controller logs would show routing info, not application health.
Detailed technical explanation
How to think about this question
Kubernetes Services use readiness probes to determine if a Pod is ready to receive traffic; only Pods passing the probe are added as endpoints. When all Pods fail readiness, the Service has zero ready endpoints, causing the Ingress controller to return 503. The `kubectl get endpoints` command can quickly confirm if endpoints exist, but the root cause is the probe failure, often due to application misconfiguration or missing dependencies.
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 CKAD 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 CKAD question in full detail.
Services and Networking — This question tests Services and Networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Check the readiness probe of the Pods — A 503 Service Unavailable error from the Ingress indicates the upstream Service is not ready to serve traffic. The most common cause is Pods failing their readiness probes, which removes them from the Service's endpoint list. Checking the readiness probe status directly addresses why the Service has endpoints but returns 503.
What should I do if I get this CKAD 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: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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