K8s Interview Questions senior/staff/principal level-2023/2024

Here are some Kubernetes interview questions and answers suitable for senior and principal level engineers, focusing on basic concepts, best practices, and configurations, is a substantial task.

1. What is Kubernetes?
   • Kubernetes is an open-source container orchestration platform for automating deployment, scaling, and management of containerized applications.
2. Describe a Kubernetes Pod.
   • A Pod is the smallest deployable unit in Kubernetes that can contain one or more containers sharing the same network and storage.
3. What is horizontal scaling in Kubernetes?
   • Horizontal scaling involves increasing the number of Pods to handle increased load, often managed by a Horizontal Pod Autoscaler.
4. List some Kubernetes deployment best practices.
   • Define resource requests and limits, use health checks, create reproducible deployments with manifests, and use namespaces for separation of concerns.
5. How should sensitive data be handled in Kubernetes?
   • Use Kubernetes Secrets to manage sensitive data like passwords and tokens, keeping them separate from Pod specifications.
6. Describe rolling updates in Kubernetes.
   • Rolling updates allow deployment updates with zero downtime, incrementally updating Pods with new versions while maintaining service availability.
7. What is a ConfigMap in Kubernetes?
   • ConfigMap stores non-confidential data in key-value pairs, used to store configuration settings and data accessible to Pods.
8. How is resource allocation managed for containers in Kubernetes?
   • Resource allocation is managed using resource requests and limits in the Pod specification, ensuring resource availability and preventing overuse.
9. Explain Kubernetes Ingress.
   • Ingress manages external access to services in a cluster, providing load balancing, SSL termination, and name-based virtual hosting.
10. What are Kubernetes Namespaces?
    • Namespaces provide a mechanism for isolating groups of resources within a single cluster, helping organize and secure multi-tenant environments.
11. How does Kubernetes Service Discovery work?
    • Service Discovery in Kubernetes is managed through services that abstract Pod IP addresses, enabling discovery and routing within the cluster.
12. Explain the role of a ReplicaSet in Kubernetes.
    • A ReplicaSet ensures that a specified number of Pod replicas are running at any given time, providing fault tolerance and scalability.
13. What is a StatefulSet in Kubernetes?
    • StatefulSets manage stateful applications, ensuring orderly deployment and scaling, and providing unique network identifiers.
14. How do Persistent Volumes work in Kubernetes?
    • Persistent Volumes provide an abstraction layer over storage resources, allowing storage to persist beyond the lifecycle of individual Pods.
15. What is a DaemonSet in Kubernetes?
    • A DaemonSet ensures that each node in the cluster runs a copy of a specific Pod, typically used for system-level operations.
16. Explain Kubernetes Labels and Selectors.
    • Labels are key-value pairs attached to objects, used for organizing and selecting subsets of objects.
17. What is a Kubernetes Deployment?
    • A Deployment provides declarative updates to Pods and ReplicaSets, managing the rollout of updates and rollbacks.
18. How do you expose a service in Kubernetes?
    • Services can be exposed using Kubernetes Service objects, Ingress, or NodePort, depending on the access requirements.
19. What is the purpose of a Kubernetes Job?
    • A Job creates one or more Pods and ensures that a specified number of them successfully terminate.
20. Explain the Kubernetes Control Plane.
    • The Control Plane is responsible for maintaining the desired state of the cluster, including scheduling and responding to cluster events.
21. How does Kubernetes handle self-healing?
    • Kubernetes automatically replaces or restarts containers that fail, ensuring the desired state of the application.
22. What are Kubernetes Resource Quotas?
    • Resource Quotas limit the total amount of resources (like CPU and memory) that can be consumed by a namespace.
23. Explain Network Policies in Kubernetes.
    • Network Policies specify how groups of Pods can communicate with each other and other network endpoints.
24. What is the Kubelet?
    • Kubelet is an agent running on each node, ensuring that containers are running in a Pod.
25. Describe the role of etcd in Kubernetes.
    • etcd is a distributed key-value store used by Kubernetes to store all cluster data, acting as the single source of truth.
26. How does Kubernetes scheduling work?
    • The Kubernetes scheduler assigns Pods to nodes based on resource requirements, node constraints, and other factors.
27. What is a Kubernetes Cluster?
    • A Kubernetes Cluster consists of at least one master and multiple worker nodes that host the components to run containerized applications.
28. Explain Kubernetes Volumes.
    • Kubernetes Volumes provide a way to persist data and share it between containers within the same Pod.
29. What are Init Containers in Kubernetes?
    • Init Containers are specialized containers that run before the main containers in a Pod, used to set up the environment or perform pre-initialization tasks.
30. How does Kubernetes manage service scaling?
    • Kubernetes scales services by adjusting the number of replicas of Pods, either manually or automatically using the Horizontal Pod Autoscaler.
31. What is the role of the Kubernetes API Server?
    • The API Server is the central management entity of Kubernetes that processes REST requests, validates them, and updates the corresponding objects in etcd.
32. Describe Kubernetes Secrets and how they differ from ConfigMaps.
    • Secrets store sensitive data such as passwords and tokens, encrypted at rest, differing from ConfigMaps which are meant for non-sensitive configuration data.
33. Explain the purpose of the Kubernetes Scheduler.
    • The Scheduler assigns Pods to Nodes based on resource availability, constraints, and affinity/anti-affinity specifications.
34. What is RBAC in Kubernetes and why is it important?
    • Role-Based Access Control (RBAC) is a method of regulating access to computer or network resources based on the roles of individual users within Kubernetes, crucial for enforcing security and access policies.
35. How do Kubernetes Probes work?
    • Probes are used to periodically check the health of a container. Liveness probes determine if an application is running, and readiness probes check if the application is ready to serve traffic.
36. What is Kubernetes Namespace isolation, and how is it implemented?
    • Namespace isolation is a way to segment cluster resources between multiple users or environments. It is implemented through Kubernetes Namespaces, each acting as a virtual cluster within the physical cluster.
37. Describe the process of rolling back a Deployment in Kubernetes.
    • Rolling back a deployment involves reverting to a previous deployment state, which Kubernetes can do by using the history of ReplicaSets and their configurations.
38. How do you monitor applications in Kubernetes?
    • Monitoring can be done using tools like Prometheus for metrics collection and Grafana for visualization. Kubernetes also provides logs and metrics through its API.
39. What are Kubernetes Taints and Tolerations?
    • Taints are applied to nodes to repel Pods unless they have a matching toleration. Tolerations allow Pods to schedule on tainted nodes.
40. Explain how Kubernetes handles storage orchestration.
    • Kubernetes automatically provisions storage when a storage request is made by a Pod, using StorageClasses to define different types of storage offered.
41. How can you manage stateful applications in Kubernetes with StatefulSets? Provide a YAML example.
    • StatefulSets are ideal for managing stateful applications, ensuring orderly and graceful deployment and scaling. They maintain a sticky identity for each of their Pods.
42. In Kubernetes, how can you auto-scale based on custom metrics?
    • To auto-scale based on custom metrics, you need to have a monitoring solution like Prometheus set up, along with the metrics-server in Kubernetes. Then, create a HorizontalPodAutoscaler that references your custom metric, specifying the metric type, name, target value, etc.
43. How can you ensure zero downtime deployments in Kubernetes?
    • Zero downtime deployments can be achieved by using rolling updates with proper readiness and liveness probes. This ensures that the new version is fully operational before the old version is terminated. Fine-tuning the rolling update strategy parameters like maxUnavailable and maxSurge is key.
44. Explain how to secure pod-to-pod communication in a Kubernetes cluster.
    • To secure pod-to-pod communication, use Network Policies to define which pods can communicate with each other. In addition, implement service mesh technologies like Istio for advanced traffic control and mTLS for encrypted communication.
45. Describe how you can use Kubernetes Volumes for sharing data between containers in a Pod. Provide a YAML example.
    • Kubernetes Volumes can be used to share data between containers within the same Pod. Here’s a simple example in YAML
46. How do you implement canary deployments in Kubernetes?
    • Canary deployments can be implemented by deploying a new version of the application alongside the stable production version but only routing a small percentage of traffic to it. This can be managed by using a combination of Deployments, Services, and Istio or a similar service mesh for traffic routing.
47. Explain how to use Kubernetes ConfigMaps for configuration without restarting the pods.
    • ConfigMaps can be used to externalize the configuration data of applications. Pods can be designed to read from ConfigMaps at runtime or use auto-reload techniques (like using sidecar containers) to detect changes in ConfigMaps without requiring a restart.
48. How do you troubleshoot a failing Pod in Kubernetes?
    • Troubleshooting a failing Pod involves checking the Pod’s events (kubectl describe pod <pod-name>), inspecting logs (kubectl logs <pod-name>), and ensuring the Pod’s resources and configurations are correctly defined. Using kubectl exec to access the container might also be necessary for deeper inspection.
49. Describe how to isolate tenants in a multi-tenant Kubernetes cluster.
    • Tenant isolation in Kubernetes can be achieved using Namespaces for soft isolation and controlling resources and access with Quotas and RBAC. For stricter isolation, network policies for inter-namespace communication and possibly even separate clusters (virtual or physical) should be considered.
50. Explain how Kubernetes handles persistent storage with StatefulSets and provide an example of a dynamic provisioning setup in YAML.
    • Kubernetes handles persistent storage in StatefulSets by using PersistentVolumeClaims (PVCs) which are automatically bound to PersistentVolumes (PVs).
51. Explain how Kubernetes handles persistent storage with StatefulSets and provide an example of a dynamic provisioning setup in YAML.
    • StatefulSets in Kubernetes use PersistentVolumeClaims (PVCs) to provide persistent storage for each pod. With dynamic provisioning, storage is automatically provisioned as needed.
52. How can you manage secret rotation in Kubernetes?
    • Secret rotation in Kubernetes can involve updating the Secret object and ensuring that applications reload the new secrets without downtime. Automating this process can involve using Kubernetes operators or external secret management systems that sync with Kubernetes Secrets.
53. Describe the use of custom resource definitions (CRDs) in extending Kubernetes functionality.
    • CRDs allow you to define custom resources to extend Kubernetes capabilities. They enable users to create new types of resources without adding them to the Kubernetes codebase, facilitating custom operator development for specific applications or services.
54. How do you manage pod placement using node affinity in Kubernetes?
    • Node affinity is a set of rules used by the scheduler to determine where pods can be placed. It allows you to constrain pod placement to specific nodes or node groups based on labels. For example, you can ensure certain pods only run on nodes with specific hardware.
55. Explain the process of setting up a Kubernetes cluster in a high-availability configuration.
    • Setting up a high-availability Kubernetes cluster involves having multiple master nodes in different zones or regions, using a reliable and distributed storage backend like etcd, and implementing load balancers or virtual IPs for master node failover.
56. How can you manage cross-cluster service discovery in Kubernetes?
    • Cross-cluster service discovery can be managed through federated Kubernetes clusters, where services in different clusters are exposed to each other. Tools like Istio’s multicluster support or CoreDNS can be used to facilitate this process.
57. What are Kubernetes operators, and how do they simplify cluster management?
    • Kubernetes operators are software extensions that use custom resources and controllers to manage complex applications. They automate routine tasks by understanding the application’s lifecycle, making it easier to manage stateful services like databases.
58. Describe the process of securing a Kubernetes cluster.
    • Securing a Kubernetes cluster involves multiple steps: ensuring cluster components are configured securely, using RBAC for access control, implementing network policies for pod communication, securing etcd, using TLS for all communications, and regularly scanning for vulnerabilities.
59. How do you implement a blue-green deployment strategy in Kubernetes?
    • In a blue-green deployment, two identical environments are maintained: one (Blue) is the current production environment, and the other (Green) is the new version. Traffic is switched from Blue to Green once the new version is ready, allowing for quick rollbacks.
60. Explain how to manage Kubernetes clusters across multiple cloud environments.
    • Managing Kubernetes across multiple clouds involves using cluster federation, where clusters in different cloud environments are joined under a single control plane. Tools like Rancher or Google Anthos can facilitate this type of management.
61. Describe the use of Helm in Kubernetes for package management.
    • Helm is a package manager for Kubernetes, which simplifies the deployment and management of applications. Helm packages, called charts, contain pre-configured Kubernetes resources that can be deployed as a single unit, streamlining complex deployments.
62. Explain the role of Container Network Interface (CNI) in Kubernetes.
    • CNI in Kubernetes is responsible for connecting pod networks to the host network. It allows Kubernetes to integrate with various networking solutions like Calico, Flannel, or Weave, providing network connectivity and isolation for Pods.
63. How can Kubernetes handle persistent storage for stateful applications?
    • Kubernetes uses Persistent Volumes (PV) and Persistent Volume Claims (PVC) to handle storage for stateful applications. PVs represent storage resources, while PVCs are requests for storage by users. Storage Classes can be used to dynamically provision PVs as per the PVCs.
64. Describe a disaster recovery plan for a Kubernetes cluster.
    • A disaster recovery plan in Kubernetes typically involves regular backups of etcd, the cluster’s datastore, as well as all critical configurations like deployments, services, and storage configurations. In case of a disaster, these backups can be used to restore the cluster’s state.
65. What are node pools in Kubernetes, and how are they used?
    • Node pools in Kubernetes are groups of nodes with the same configuration. They are used in cloud environments to manage different types of worker nodes separately, such as those with different CPU, memory, or storage capacities, or those in different geographical regions.
66. How do you perform a rolling restart of deployments in Kubernetes?
    • A rolling restart in Kubernetes can be performed by updating the deployment with a minor change, such as updating an environment variable or a label. This triggers a rolling update, which restarts all pods in the deployment without changing the actual application version.
67. Explain the different types of services in Kubernetes.
    • Kubernetes offers several types of services:
      • ClusterIP: Exposes the service on an internal IP in the cluster, making it only reachable from within the cluster.
      • NodePort: Exposes the service on the same port of each selected Node in the cluster using NAT, making it accessible from outside the cluster.
      • LoadBalancer: Creates an external load balancer in the current cloud (if supported) and assigns a fixed, external IP to the service.
      • ExternalName: Maps a service to a DNS name, rather than to a typical selector such as my-service.
68. How does Kubernetes integrate with CNI plugins for network policies?
    • Kubernetes integrates with CNI plugins to enforce network policies, which control the flow of traffic between pod groups. CNI plugins like Calico or Cilium can be used to implement these policies, providing features like ingress and egress filtering based on pod labels and network CIDRs.
69. What strategies can be employed for efficient storage management in Kubernetes?
    • Efficient storage management strategies in Kubernetes include using dynamic provisioning with StorageClasses to automatically create storage as needed, implementing StatefulSets for stateful applications, leveraging Persistent Volume Claims for storage scaling, and employing proper backup and recovery procedures.
70. Describe a method to ensure high availability of services in Kubernetes.
    • To ensure high availability of services, you can use multiple replicas of Pods across different nodes and availability zones. Employing a LoadBalancer type service or an Ingress controller can distribute traffic across these replicas. Monitoring and auto-scaling can also help maintain availability under varying loads.
71. How would you set up and use a ReadWriteMany Persistent Volume in Kubernetes?
    • To set up a ReadWriteMany Persistent Volume in Kubernetes, you would choose a storage solution that supports RWX access mode, like NFS or a cloud-based file store. Define a PersistentVolume with the ReadWriteMany access mode, and then create a PersistentVolumeClaim to claim storage from this volume for use by Pods.
72. Explain how node pool upgrades are handled in Kubernetes.
    • Node pool upgrades in Kubernetes typically involve creating a new node pool with the updated configuration or Kubernetes version, then gradually draining and replacing the nodes in the old node pool with nodes from the new pool to ensure minimal disruption to running applications.
73. What is the best practice for managing Kubernetes secrets?
    • Best practices for managing Kubernetes secrets include limiting access using RBAC, avoiding storing secrets in Pod specs or scripts, using external secret management tools like HashiCorp Vault, and encrypting secrets at rest and in transit.
74. How can you ensure data resiliency and disaster recovery for stateful applications in Kubernetes?
    • For data resiliency and disaster recovery in Kubernetes, regularly back up etcd and persistent data, replicate data across multiple zones or clusters, and have a clear recovery plan. Tools like Velero can be used for backup and restore processes.
75. Describe the process of scaling a node pool in a cloud Kubernetes service.
    • Scaling a node pool in a cloud Kubernetes service can typically be done through the cloud provider’s management console or CLI. It involves either manually adjusting the number of nodes or setting up auto-scaling based on resource usage metrics.
76. How do you handle rolling restarts for stateful applications in Kubernetes?
    • Rolling restarts for stateful applications should be handled carefully to maintain data consistency. Use StatefulSets with a proper update strategy and ensure that each pod is fully operational before moving to the next one. Implement readiness probes to ensure zero downtime.