Kubernetes¶

Kubernetes (K8s) orchestrates containerized applications — automating deployment, scaling, and management. Key concepts: Pod (smallest deployable unit, 1+ containers), Deployment (manages replica sets), Service (stable networking for pods), ConfigMap/Secret (configuration), Ingress (HTTP routing). K8s ensures desired state: if a pod dies, it's automatically replaced.

Key Concepts¶

Deep Dive: Core Architecture

┌──────────────── Control Plane ──────────────────┐
│  API Server → etcd (state store)                │
│  Scheduler → Controller Manager                 │
└─────────────────────┬───────────────────────────┘
                      │
┌─────── Worker Node 1 ───────┐  ┌─── Worker Node 2 ───┐
│  kubelet  │  kube-proxy     │  │  kubelet  │ kube-proxy│
│  ┌─────┐  ┌─────┐          │  │  ┌─────┐             │
│  │Pod A│  │Pod B│          │  │  │Pod C│             │
│  └─────┘  └─────┘          │  │  └─────┘             │
└─────────────────────────────┘  └─────────────────────┘

Deep Dive: Key Resources

Deployment:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-app
        image: my-app:1.0
        ports:
        - containerPort: 8080
        resources:
          requests:
            memory: "256Mi"
            cpu: "250m"
          limits:
            memory: "512Mi"
            cpu: "500m"

Service (ClusterIP, NodePort, LoadBalancer):

apiVersion: v1
kind: Service
metadata:
  name: my-app-service
spec:
  type: ClusterIP
  selector:
    app: my-app
  ports:
  - port: 80
    targetPort: 8080

Deep Dive: Scaling & Self-Healing

# Manual scaling
kubectl scale deployment my-app --replicas=5

# Auto-scaling
kubectl autoscale deployment my-app --min=2 --max=10 --cpu-percent=80

Self-healing: If a pod crashes, the Deployment controller creates a replacement. Rolling update: Gradually replaces old pods with new ones (zero downtime). Rollback: kubectl rollout undo deployment my-app

Common Interview Questions

What is Kubernetes? What problem does it solve?
What is a Pod? How is it different from a container?
What is a Deployment? What is a ReplicaSet?
What are Service types (ClusterIP, NodePort, LoadBalancer)?
What is an Ingress?
How does K8s handle scaling?
What is a ConfigMap/Secret?
How does K8s ensure high availability?