Docker and Kubernetes are essential DevOps skills in 2026. Every cloud and backend engineering role requires containerization and orchestration knowledge. These top 10 Docker and Kubernetes interview questions will help you ace your DevOps interview.

Keywords: Docker interview questions 2026, Kubernetes interview, DevOps interview prep, container orchestration, K8s interview questions

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1. What is Docker and how does it work?

Docker is a platform for building, shipping, and running applications in containers. Containers are lightweight, portable, and isolated environments that share the host OS kernel. Docker uses images as templates to create containers with all dependencies packaged together.

2. What is the difference between a Docker image and a container?

A Docker image is a read-only template containing application code, libraries, and dependencies. A container is a running instance of an image. Multiple containers can be created from a single image. Images are built using Dockerfiles and stored in registries.

3. What is a Dockerfile and how do you optimize it?

A Dockerfile contains instructions to build a Docker image. Optimize by using multi-stage builds, minimizing layers, using slim base images, leveraging build cache, copying only necessary files, and running as non-root user. Use .dockerignore to exclude unnecessary files.

4. What is Docker Compose?

Docker Compose is a tool for defining and running multi-container applications using a YAML file. It manages service dependencies, networking, and volumes. Use docker-compose up to start all services and docker-compose down to stop them. Ideal for local development environments.

5. What is Kubernetes and why is it needed?

Kubernetes is an open-source container orchestration platform that automates deployment, scaling, and management of containerized applications. It handles load balancing, service discovery, self-healing, rolling updates, and secret management across clusters of machines.

6. Explain Kubernetes Pods, Deployments, and Services.

A Pod is the smallest deployable unit containing one or more containers. A Deployment manages Pod replicas and handles rolling updates and rollbacks. A Service provides stable networking and load balancing for Pods. Together they form the core Kubernetes architecture.

7. What are Kubernetes namespaces?

Namespaces provide logical isolation within a Kubernetes cluster. They allow multiple teams to share a cluster while keeping resources separated. Default namespaces include default, kube-system, and kube-public. Use namespaces for environment separation and resource quotas.

8. How does Kubernetes handle scaling?

Kubernetes supports horizontal pod autoscaling based on CPU, memory, or custom metrics. Vertical pod autoscaling adjusts resource requests. Cluster autoscaler adds or removes nodes. Use Horizontal Pod Autoscaler (HPA) for automatic scaling based on demand.

9. What are ConfigMaps and Secrets in Kubernetes?

ConfigMaps store non-sensitive configuration data as key-value pairs. Secrets store sensitive data like passwords and API keys in base64 encoded format. Both can be mounted as volumes or environment variables. Use external secret managers for production security.

10. How do you troubleshoot a failing Kubernetes Pod?

Use kubectl describe pod to check events and status. Use kubectl logs to view container logs. Check resource limits and requests. Verify image availability and pull secrets. Use kubectl exec to access the container shell. Check liveness and readiness probes configuration.

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Conclusion: Docker and Kubernetes are must-know technologies for DevOps and cloud engineering roles. Practice building containers, deploying to clusters, and troubleshooting to excel in interviews.

Tags: #Docker #Kubernetes #DevOps #InterviewQuestions #Containerization #K8s #CloudEngineering #CICD #Microservices #DevOps2026