KCNA Practice Test 7 — 10 Questions

Question 1

You want to run a batch job that processes a queue and then terminates. Which Kubernetes resource should you use?

Accepted Answer

Job. A Kubernetes Job is designed for batch processing tasks that run to completion and then terminate. It creates one or more Pods and ensures they successfully finish executing a specific workload, making it the correct choice for processing a queue and then exiting.

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Deployment

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CronJob

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DaemonSet

Question 2

What is the purpose of a Service in Kubernetes?

Accepted Answer

To expose a set of pods as a network service with a stable endpoint. A Service in Kubernetes provides a stable network endpoint (IP address and DNS name) to access a set of Pods, which are ephemeral and can be created or destroyed dynamically. It decouples the client from the Pods' IPs by using label selectors to route traffic, enabling reliable communication within the cluster or externally. This is defined in the Kubernetes API as a Service resource, with types like ClusterIP, NodePort, and LoadBalancer.

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To provide persistent storage volumes

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To manage rolling updates of pods

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To store configuration data as key-value pairs

Question 3

What is the primary benefit of using containers over virtual machines?

Accepted Answer

Containers are lightweight and share the host OS kernel. Containers are lightweight because they share the host OS kernel, avoiding the overhead of a separate guest OS per instance. Unlike VMs, which require a hypervisor and a full OS for each virtual machine, containers run as isolated processes on the same kernel, enabling faster startup times and higher density. This shared-kernel model is the primary benefit, as it reduces resource consumption and improves efficiency in orchestrated environments like Kubernetes.

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Containers provide stronger isolation between applications

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Containers include a full operating system per instance

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Containers require a hypervisor to run

Question 4

You want to update a Deployment's container image to v2 and perform a rolling update using the simplest imperative command. Which kubectl command achieves this?

Accepted Answer

kubectl set image deployment/my-deployment my-container=myapp:v2 --record. The `kubectl set image` command is the standard imperative way to update a container image in a Deployment, and it automatically triggers a rolling update. Option A is invalid; `kubectl update` is not a real command. Option B, `kubectl replace`, requires a full YAML file and is a declarative replacement operation, not a simple image update command. Option C, `kubectl patch`, can be used but is overly complex and error-prone for a simple image update. The question asks for the simplest imperative command, making D the best answer.

Answer

kubectl update deployment my-deployment --image=myapp:v2

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kubectl replace -f updated-deployment.yaml

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kubectl patch deployment my-deployment -p '{"spec":{"template":{"spec":{"containers":[{"name":"my-container","image":"myapp:v2"}]}}}}'

Question 5

Which component in an event-driven architecture is responsible for decoupling event producers from consumers?

Accepted Answer

Event broker. The event broker (e.g., Kafka, RabbitMQ, NATS) is the central component that receives events from producers and routes them to consumers, allowing producers and consumers to operate independently without direct knowledge of each other. It provides asynchronous, decoupled communication by buffering events, managing subscriptions, and ensuring delivery. This decoupling enables scalability, fault tolerance, and independent evolution of services.

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Config server

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API gateway

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Service mesh

Question 6

Which control plane component is responsible for assigning pods to nodes?

Accepted Answer

kube-scheduler. The kube-scheduler is the control plane component responsible for assigning pods to nodes. It watches for newly created pods that have no node assignment and selects an optimal node for each pod based on resource requirements, constraints, policies, and data locality. The scheduler does not actually run the pod; it updates the pod's `nodeName` field via the API server, which then triggers the kubelet on the chosen node to launch the pod.

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etcd

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kube-apiserver

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kube-controller-manager

Question 7

What is the main advantage of using OpenTelemetry over vendor-specific instrumentation libraries?

Accepted Answer

It provides a single, vendor-agnostic instrumentation standard. OpenTelemetry provides a unified standard that avoids vendor lock-in, allowing data to be sent to any backend.

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It eliminates the need for logging

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It automatically reduces latency

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It is the only tool that supports traces

Question 8

A developer wants to ensure that a pod runs only on nodes with SSDs. Which mechanism should be used?

Accepted Answer

Add a nodeSelector with disktype: ssd. `nodeSelector` is a simple and direct mechanism in Kubernetes to constrain a pod to run only on nodes that have a specific label, such as `disktype=ssd`. By labeling nodes with SSDs and adding the corresponding `nodeSelector` in the pod spec, the scheduler ensures the pod is placed exclusively on those nodes. This approach is straightforward and does not require complex scheduling constraints or resource management.

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Apply a taint to nodes without SSDs and add tolerations to the pod

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Use pod anti-affinity

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Define a ResourceQuota

Question 9

You need to run a batch job that processes a queue and then terminates. Which Kubernetes resource should you use?

Accepted Answer

Job. A Job is the correct Kubernetes resource for running a batch process that executes a finite task (e.g., processing a queue) and then terminates. Unlike controllers that maintain a desired state indefinitely, a Job creates one or more Pods and ensures they run to successful completion, after which the Job itself completes and no further Pods are created.

Answer

Deployment

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DaemonSet

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StatefulSet

Question 10

A team wants to deploy a stateful application that requires each pod to have a unique, stable network identity and persistent storage that persists across rescheduling. Which Kubernetes resource is most appropriate?

Accepted Answer

StatefulSet. StatefulSet is the correct choice because it provides each pod with a unique, stable network identity (via a predictable hostname derived from the StatefulSet name and ordinal index) and dedicated persistent storage that persists across rescheduling. This is achieved through a headless Service and PersistentVolumeClaims (PVCs) that are bound to each pod's identity, ensuring that when a pod is rescheduled, it reattaches to the same storage and retains its network identity.

Answer

DaemonSet

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Deployment

Answer

Job