KCNA Cloud Native Application Delivery Practice Question
In Kustomize, what is the purpose of an overlay?
⚠ Common exam trap
KCNA often tests the distinction between Kustomize overlays and Helm templating, causing candidates to confuse variable substitution with overlay-based customization.
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
✓
To apply environment-specific customizations on top of a base
In Kustomize, an overlay is a kustomization that references a base and applies environment-specific customizations such as patches, name prefixes, or label changes. This allows you to reuse a common base configuration while tailoring it for different environments like dev, staging, and prod. The overlay does not modify the base itself; it produces a new set of resources with the changes applied.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
To apply environment-specific customizations on top of a base
Why this is correct
An overlay is a Kustomization layered over a base, patching or adding resources so the same base yields environment-specific output such as dev or production variants. This satisfies the requirement to customise a shared base per environment.
- ✗
To merge multiple Kubernetes manifests into one
Why it's wrong here
Kustomize builds a resource list from a kustomization.yaml referencing other files; it does not concatenate arbitrary manifests into one document. Merging manifests is tempting because overlays do combine base and patch content, but that combination is strategic-merge patching of declared resources, not generic file merging.
- ✗
To template variables into YAML files
Why it's wrong here
Kustomize performs structured patching of YAML fields; it has no templating engine, so variables and conditionals are unsupported. Templating is tempting because overlays vary values per environment, but that variation comes from patch files and name prefixes or suffixes, not placeholder substitution.
- ✗
To define the base configuration of an application
Why it's wrong here
A base holds the shared, environment-agnostic resources and kustomization.yaml that overlays reference; defining it is the base's job, not the overlay's. Overlays are tempting here because they also contain kustomization.yaml files, but an overlay layers environment-specific patches on top of a base rather than establishing it.
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Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CNCF exam blueprint
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