KCNA Cloud Native Architecture Practice Question
Which Kubernetes resource is commonly used to implement the sidecar pattern for injecting a service mesh proxy?
⚠ Common exam trap
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.
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
✓
MutatingAdmissionWebhook
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.
Answer analysis
Option-by-option breakdown
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.
- ✗
ConfigMap
Why it's wrong here
ConfigMaps store configuration data, not inject sidecars.
Go deeper
Related to this question
Learn chapter
Kubernetes Overview and Core Components
Key term
ReplicaSet and Replication
A ReplicaSet ensures a specified number of identical pod instances are running at all times in Kubernetes, using replication to maintain availability and stability.
Key term
Service Mesh
A service mesh is a dedicated infrastructure layer that manages communication between microservices, handling tasks like service discovery, load balancing, encryption, and observability without requiring changes to application code.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.