KCNA Practice Test 3 — 25 Questions

Question 1

Which THREE of the following are valid use cases for distributed tracing in a microservices architecture?

Accepted Answer

Understanding the dependency graph between microservices. Distributed tracing is designed to follow a single request as it propagates across service boundaries, so option B is correct because the spans and parent-child relationships recorded in a trace directly reveal the dependency graph and call topology between microservices. Option C is correct because a trace correlates spans across services with shared trace IDs, letting you locate the exact failing span and thus the root cause of an error in a distributed transaction. Option D is correct because span durations and timestamps expose per-service latency contributions, making it possible to identify which service adds the most latency to an end-user request. Option A is not a tracing use case; CPU and memory usage per instance are collected by metrics/monitoring tools such as Prometheus or CloudWatch, not by distributed tracing. Option E is also not specific to tracing; detailed error messages and stack traces are typically captured by centralized logging or error-tracking systems, even though traces may carry limited error tags.

Answer

Monitoring CPU and memory usage of each service instance

Answer

Capturing detailed error messages and stack traces

Question 2

A user runs 'kubectl create deployment my-deploy --image=nginx' and then wants to scale the deployment to 5 replicas. Which command should they use?

Accepted Answer

kubectl scale deployment my-deploy --replicas=5. `kubectl scale` is the dedicated imperative command to change the replica count of a deployment. It directly updates the `spec.replicas` field in the deployment's desired state, and the deployment controller then adjusts the ReplicaSet and Pods accordingly. This is the simplest and most direct way to scale a deployment without modifying a YAML file or using an editor.

Answer

kubectl apply -f deployment.yaml with replicas: 5

Answer

kubectl edit deployment my-deploy and change replicas to 5

Answer

kubectl patch deployment my-deploy -p '{"spec":{"replicas":5}}'

Question 3

Which TWO of the following are functions of the kube-controller-manager?

Accepted Answer

Managing replication and ensuring the desired number of pods are running. Option A is correct because the kube-controller-manager runs the ReplicationController/ReplicaSet controller, which continuously reconciles the actual number of running pods with the desired replica count specified in the resource. Option D is correct because the kube-controller-manager includes the node controller, which monitors node health via heartbeats/leases and responds to node failures by marking nodes NotReady and evicting or rescheduling their pods. Option B is incorrect because cluster state is persisted in etcd, not by the kube-controller-manager. Option C is incorrect because the Kubernetes API is exposed by the kube-apiserver. Option E is incorrect because pod-to-node assignment (scheduling) is performed by the kube-scheduler.

Answer

Storing cluster state

Answer

Exposing the Kubernetes API

Answer

Assigning pods to nodes

Question 4

Which THREE are benefits of using container orchestration platforms like Kubernetes?

Accepted Answer

High availability through automatic container restart and replication. Option A is correct because Kubernetes provides high availability by automatically restarting failed containers and maintaining the desired number of replicas across nodes, ensuring workloads remain available even when individual containers or nodes fail. Option B is correct because Kubernetes supports automatic scaling of container replicas through mechanisms like the Horizontal Pod Autoscaler, which adjusts replica counts based on observed CPU, memory, or custom metrics. Option C is correct because Kubernetes performs self-healing by detecting failed containers, pods, or nodes and replacing or rescheduling them without manual intervention, restoring the declared desired state. Option D is not a benefit of orchestration because Kubernetes manages deployment and runtime concerns, not application source code, so developers still must write and modify code as needed. Option E is incorrect because orchestration platforms do not eliminate monitoring and logging; they integrate with tools like Prometheus, Grafana, and the ELK stack, and observability remains essential for operating containerized workloads.

Answer

Simplified application development by eliminating the need for code changes

Answer

Elimination of the need for monitoring and logging

Question 5

Which command is used to view the logs of a pod named 'web-pod'?

Accepted Answer

kubectl logs web-pod. The correct command to view logs from a pod in Kubernetes is 'kubectl logs web-pod'. This command retrieves the current stdout/stderr output from the primary container in the specified pod, which is the standard method for accessing container logs without entering the pod.

Answer

kubectl describe pod web-pod

Answer

kubectl get logs web-pod

Answer

kubectl exec web-pod -- logs

Question 6

You have a Deployment with the following rollout strategy: rollingUpdate: maxSurge: 1, maxUnavailable: 0. What behavior does this configuration enforce?

Accepted Answer

The rollout will create one additional pod before terminating the old pod, ensuring zero downtime. The rolling update strategy `maxSurge: 1, maxUnavailable: 0` ensures that during the rollout, one additional pod is created above the desired replica count before any existing pod is terminated. This guarantees that the total number of available pods never drops below the desired count, achieving zero downtime. The `maxUnavailable: 0` setting prevents any pod from being taken down until a new one is ready, while `maxSurge: 1` allows one extra pod to be created temporarily.

Answer

The rollout will terminate all old pods at once and then create new ones

Answer

The rollout will create all new pods first, then delete all old pods

Answer

The rollout will terminate one old pod before creating a new one

Question 7

What is the function of kube-proxy on a worker node?

Accepted Answer

It implements part of the Kubernetes Service concept by managing network rules. kube-proxy runs on each worker node and is responsible for implementing the Kubernetes Service abstraction by managing network rules (e.g., iptables, IPVS, or userspace mode). It watches the API server for Service and EndpointSlice changes and configures local packet filtering or forwarding rules to route traffic to the correct backend pods, enabling load balancing and service discovery.

Answer

It ensures the desired number of pods are running

Answer

It runs the container runtime

Answer

It reports node status to the control plane

Question 8

A user creates a Deployment with 'replicas: 3'. After applying the manifest, only 2 pods are running. What is the most likely cause?

Accepted Answer

There is insufficient node capacity to schedule the third pod. The most likely cause is insufficient node capacity, as the scheduler cannot place the third pod due to resource constraints (CPU, memory, or other limits). The Deployment controller creates a ReplicaSet, which instructs the scheduler to place pods; if nodes lack sufficient allocatable resources, pods remain in Pending state. This is a common scenario when cluster resources are exhausted.

Answer

The Deployment's YAML had a syntax error

Answer

The container image name is misspelled

Answer

The ReplicaSet controller is not running

Question 9

A microservice application is experiencing high latency during traffic spikes. The team identifies that the database connection pool is exhausted. They want to implement a pattern that helps decouple the microservice from direct database connections and smooth out traffic bursts. Which design pattern should they apply?

Accepted Answer

Queue-based Load Leveling pattern. The Queue-based Load Leveling pattern uses a message queue (e.g., RabbitMQ, Amazon SQS) as a buffer between the microservice and the database. When traffic spikes occur, requests are queued and processed at a manageable rate, preventing the database connection pool from being exhausted. This decouples the service from direct database connections and smooths out bursts, directly addressing the latency issue.

Answer

Bulkhead pattern

Answer

Circuit Breaker pattern

Answer

Retry pattern

Question 10

Which of the following is true about Kubernetes Namespaces?

Accepted Answer

Namespaces are used to logically isolate resources like pods and services. Kubernetes Namespaces provide a mechanism to logically isolate resources such as Pods, Services, and Deployments within a single cluster. They enable multi-tenancy by partitioning cluster resources among multiple users or teams, each operating within their own virtual cluster. This logical isolation does not include network segmentation by default, but it allows for resource quota enforcement and access control via RBAC.

Answer

Namespaces can be nested

Answer

Namespaces are required for all resources

Answer

Namespaces provide network isolation by default

Question 11

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.

Answer

Deployment

Answer

CronJob

Answer

DaemonSet

Question 12

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.

Answer

To provide persistent storage volumes

Answer

To manage rolling updates of pods

Answer

To store configuration data as key-value pairs

Question 13

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.

Answer

Containers provide stronger isolation between applications

Answer

Containers include a full operating system per instance

Answer

Containers require a hypervisor to run

Question 14

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

Answer

kubectl replace -f updated-deployment.yaml

Answer

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

Question 15

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.

Answer

Config server

Answer

API gateway

Answer

Service mesh

Question 16

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.

Answer

etcd

Answer

kube-apiserver

Answer

kube-controller-manager

Question 17

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.

Answer

It eliminates the need for logging

Answer

It automatically reduces latency

Answer

It is the only tool that supports traces

Question 18

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.

Answer

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

Answer

Use pod anti-affinity

Answer

Define a ResourceQuota

Question 19

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

Answer

DaemonSet

Answer

StatefulSet

Question 20

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

Answer

Deployment

Answer

Job