Kubernetes Interview Questions & Answers (2024)

What is Kubernetes and what are its core components?

Basic

Kubernetes (K8s) is an open-source container orchestration platform that automates deployment, scaling, and management of containerized applications.

Control Plane components:

kube-apiserver — HTTP API gateway; all interactions go through here
etcd — distributed key-value store; source of truth for cluster state
kube-scheduler — assigns Pods to nodes based on resource requirements
kube-controller-manager — runs controllers (ReplicaSet, Deployment, Node, etc.)
cloud-controller-manager — integrates with cloud provider (AWS, GCP, Azure)

Worker Node components:

kubelet — agent on each node; ensures containers run as specified
kube-proxy — network proxy; implements Service virtual IPs
Container Runtime — runs containers (containerd, CRI-O)

What is the difference between a Pod, Deployment, and StatefulSet?

Basic

Pod — smallest deployable unit; 1+ containers sharing network and storage

# Ephemeral — if deleted, not recreated
apiVersion: v1
kind: Pod
spec:
  containers:
  - name: app
    image: nginx:1.25

Deployment — manages stateless Pods; supports rolling updates and rollback

apiVersion: apps/v1
kind: Deployment
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0

StatefulSet — for stateful apps (databases)

Pods get stable names: postgres-0, postgres-1, postgres-2
Ordered startup/shutdown (0→1→2)
Persistent volumes survive pod restarts

DaemonSet — runs one pod per node (log collectors, monitoring agents) Job / CronJob — run-to-completion tasks; scheduled tasks

Explain the types of Kubernetes Services.

Basic

Type	Scope	Use Case
ClusterIP	Internal cluster only	Service-to-service communication
NodePort	`<NodeIP>:<30000-32767>`	Dev/test direct access
LoadBalancer	Cloud LB (ELB, GLB)	Production external traffic
ExternalName	DNS CNAME alias	Pointing to external services

# Production LoadBalancer (AWS NLB)
apiVersion: v1
kind: Service
metadata:
  name: web-svc
  annotations:
    service.beta.kubernetes.io/aws-load-balancer-type: "nlb"
    service.beta.kubernetes.io/aws-load-balancer-scheme: "internet-facing"
spec:
  type: LoadBalancer
  selector:
    app: web
  ports:
  - port: 443
    targetPort: 8080

How does Kubernetes RBAC work? Create a read-only service account.

Intermediate

RBAC (Role-Based Access Control) restricts what users and service accounts can do.

Objects:

Role — namespace-scoped permissions
ClusterRole — cluster-wide permissions
RoleBinding — bind Role to subjects in a namespace
ClusterRoleBinding — bind ClusterRole cluster-wide

# 1. Create Role with read-only permissions
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: pod-reader
  namespace: production
rules:
- apiGroups: [""]
  resources: ["pods", "pods/log", "services", "endpoints"]
  verbs: ["get", "list", "watch"]
- apiGroups: ["apps"]
  resources: ["deployments", "replicasets"]
  verbs: ["get", "list", "watch"]

---
# 2. Bind to a service account
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: pod-reader-binding
  namespace: production
subjects:
- kind: ServiceAccount
  name: monitoring-sa
  namespace: monitoring
roleRef:
  kind: Role
  name: pod-reader
  apiGroup: rbac.authorization.k8s.io

# Verify permissions
kubectl auth can-i list pods -n production --as=system:serviceaccount:monitoring:monitoring-sa
# yes

kubectl auth can-i delete pods -n production --as=system:serviceaccount:monitoring:monitoring-sa
# no

How does HorizontalPodAutoscaler (HPA) work?

Intermediate

HPA automatically adjusts Pod replicas based on observed metrics.

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: web-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: web
  minReplicas: 2
  maxReplicas: 20
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 60
  - type: Resource
    resource:
      name: memory
      target:
        type: AverageValue
        averageValue: 512Mi
  behavior:
    scaleUp:
      stabilizationWindowSeconds: 60
      policies:
      - type: Pods
        value: 4
        periodSeconds: 60
    scaleDown:
      stabilizationWindowSeconds: 300  # Wait 5 min before scaling down

Requirements: Metrics Server must be running; Pods must define resource requests.

VPA (Vertical Pod Autoscaler) automatically adjusts CPU/memory requests — complementary to HPA.

How do you troubleshoot a Pod stuck in CrashLoopBackOff?

Advanced

CrashLoopBackOff = container starts, crashes, K8s restarts it — in a loop.

Systematic diagnosis:

# 1. Describe pod — check Events section
kubectl describe pod <name> -n <ns>

# 2. Current logs
kubectl logs <name> -n <ns>

# 3. Previous container logs (before crash)
kubectl logs <name> -n <ns> --previous

# 4. Resource usage
kubectl top pod <name> -n <ns>

Common causes:

Symptom	Cause	Fix
Exit code 137	OOMKilled	Increase memory limit
“executable not found”	Wrong CMD	Fix `command:` in spec
“connection refused”	DB/dep not ready	Add `initContainers` or retry logic
“file not found”	Missing ConfigMap mount	Create ConfigMap/Secret
Liveness probe failing	App slow to start	Increase `initialDelaySeconds`

# Debug: run container with override command
kubectl run debug --image=<same-image> -it --rm --restart=Never \
  --command -- /bin/sh

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