This KCNA practice question tests your understanding of cloud native architecture. 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.
Which Kubernetes resource is commonly used to implement the sidecar pattern for injecting a service mesh proxy?
NetworkPolicy
Why wrong: NetworkPolicy controls traffic, not injection.
Service
Why wrong: Services expose pods, but do not inject sidecars.
MutatingAdmissionWebhook
Service meshes like Istio use a mutating webhook to automatically inject the Envoy sidecar proxy.
ConfigMap
Why wrong: ConfigMaps store configuration data, not inject sidecars.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
MutatingAdmissionWebhook
Option C is correct because a MutatingAdmissionWebhook intercepts Pod creation requests and automatically injects a sidecar container (e.g., Envoy or Linkerd-proxy) into the Pod spec. This is the standard mechanism used by service mesh control planes like Istio and Linkerd to transparently add the proxy without modifying application manifests.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
NetworkPolicy
Why it's wrong here
NetworkPolicy controls traffic, not injection.
Service
Why it's wrong here
Services expose pods, but do not inject sidecars.
MutatingAdmissionWebhook
Why this is correct
Service meshes like Istio use a mutating webhook to automatically inject the Envoy sidecar proxy.
Related concept
Read the scenario before looking for a memorised answer.
ConfigMap
Why it's wrong here
ConfigMaps store configuration data, not inject sidecars.
Common exam traps
CNCF often tests the misconception that a Service or NetworkPolicy is responsible for sidecar injection, when in fact only a mutating admission webhook can automatically modify Pod specs at creation time.
Detailed technical explanation
Under the hood, the MutatingAdmissionWebhook is called by the kube-apiserver before the Pod is persisted; it receives an AdmissionReview JSON object and returns a JSON Patch (RFC 6902) that adds the sidecar container, volumes, and environment variables. In Istio, the webhook is configured via a ValidatingWebhookConfiguration and MutatingWebhookConfiguration, and the sidecar proxy uses iptables rules to intercept all inbound and outbound traffic via a redirect to the proxy’s port (e.g., 15001 for Envoy).
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Cloud Native Architecture — study guide chapter
Learn the concepts, then practise the questions
Cloud Native Architecture practice questions
Targeted practice on this topic area only
All KCNA questions
997 questions across all exam domains
Kubernetes and Cloud Native Associate KCNA study guide
Full concept coverage aligned to exam objectives
KCNA practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Practise KCNA questions linked to Kubernetes Fundamentals.
Practise KCNA questions linked to Container Orchestration.
Practise KCNA questions linked to Cloud Native Architecture.
Practise KCNA questions linked to Cloud Native Observability.
Practise KCNA questions linked to Cloud Native Application Delivery.
Practise KCNA questions linked to KCNA fundamentals.
Practise KCNA questions linked to KCNA scenario.
Practise KCNA questions linked to KCNA troubleshooting.
Practice this exam
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Cloud Native Architecture — This question tests Cloud Native Architecture — Read the scenario before looking for a memorised answer..
The correct answer is: MutatingAdmissionWebhook — Option C is correct because a MutatingAdmissionWebhook intercepts Pod creation requests and automatically injects a sidecar container (e.g., Envoy or Linkerd-proxy) into the Pod spec. This is the standard mechanism used by service mesh control planes like Istio and Linkerd to transparently add the proxy without modifying application manifests.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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 →
Keep practising
Last reviewed: Jun 30, 2026
This KCNA 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 KCNA 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.