Docker to Kubernetes: Container Orchestration in Production

Containers revolutionized how we package and deploy software. Docker made them accessible, and Kubernetes made them manageable at scale. But the gap between "hello world on Docker" and "production Kubernetes" is substantial. This guide covers the journey — from Docker fundamentals to production-grade Kubernetes deployments with GitOps.

Docker Fundamentals

Multi-Stage Builds

Multi-stage builds keep your images small by separating build dependencies from runtime:

# Stage 1: Build
FROM node:22-alpine AS builder
WORKDIR /app
COPY package.json pnpm-lock.yaml ./
RUN corepack enable && pnpm install --frozen-lockfile
COPY . .
RUN pnpm build

# Stage 2: Production runtime
FROM node:22-alpine
RUN addgroup -S app && adduser -S app -G app
WORKDIR /app
COPY --from=builder /app/.next ./.next
COPY --from=builder /app/public ./public
COPY --from=builder /app/package.json ./
COPY --from=builder /app/node_modules ./node_modules
USER app
EXPOSE 3000
CMD ["node_modules/.bin/next", "start"]

Key practices:

• Use specific tags, never :latest in production
• Run as non-root user
• Minimize layers by combining RUN commands
• Use .dockerignore to exclude node_modules, .git, build artifacts

Docker Compose for Development

# docker-compose.yml
services:
  app:
    build:
      context: .
      target: builder
    ports: ["3000:3000"]
    volumes:
      - .:/app
      - /app/node_modules
    environment:
      - DATABASE_URL=postgresql://app:dev@db:5432/app
    depends_on:
      db:
        condition: service_healthy

  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_USER: app
      POSTGRES_PASSWORD: dev
      POSTGRES_DB: app
    volumes:
      - pgdata:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U app"]
      interval: 5s
      timeout: 3s
      retries: 5

  redis:
    image: redis:7-alpine
    ports: ["6379:6379"]

volumes:
  pgdata:

Kubernetes Architecture

Kubernetes abstracts your infrastructure into a unified API. The key resources:

Cluster
└── Namespace
    ├── Deployment (manages Pods)
    │   └── ReplicaSet
    │       └── Pod (smallest deployable unit)
    │           └── Container(s)
    ├── Service (stable network endpoint)
    ├── Ingress (HTTP routing)
    ├── ConfigMap (configuration)
    └── Secret (sensitive data)

Deployment

# k8s/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app
  namespace: production
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: app
        image: registry.example.com/app:v1.2.3
        ports:
        - containerPort: 3000
        resources:
          requests:
            cpu: 250m
            memory: 256Mi
          limits:
            cpu: 1000m
            memory: 512Mi
        readinessProbe:
          httpGet:
            path: /api/health
            port: 3000
          initialDelaySeconds: 5
          periodSeconds: 5
        livenessProbe:
          httpGet:
            path: /api/health
            port: 3000
          initialDelaySeconds: 15
          periodSeconds: 20
        envFrom:
        - configMapRef:
            name: app-config
        - secretRef:
            name: app-secrets

Service

apiVersion: v1
kind: Service
metadata:
  name: app-service
  namespace: production
spec:
  selector:
    app: my-app
  ports:
  - port: 80
    targetPort: 3000
  type: ClusterIP

Ingress with TLS

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: app-ingress
  namespace: production
  annotations:
    cert-manager.io/cluster-issuer: letsencrypt-prod
    nginx.ingress.kubernetes.io/ssl-redirect: "true"
spec:
  tls:
  - hosts:
    - app.example.com
    secretName: app-tls
  rules:
  - host: app.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: app-service
            port:
              number: 80

Resource Management

# Horizontal Pod Autoscaler
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: app-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: app
  minReplicas: 3
  maxReplicas: 20
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 70
  - type: Resource
    resource:
      name: memory
      target:
        type: Utilization
        averageUtilization: 80

GitOps with ArgoCD

ArgoCD continuously syncs your Kubernetes manifests from Git — your repo is the source of truth.

# argocd/application.yaml
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: my-app
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/itsmawja/my-app
    targetRevision: main
    path: k8s/overlays/production
  destination:
    server: https://kubernetes.default.svc
    namespace: production
  syncPolicy:
    automated:
      prune: true
      selfHeal: true
    syncOptions:
    - CreateNamespace=true

With this setup:

• Push to main → ArgoCD detects the change → applies to cluster
• Drift detection: if someone manually changes a resource, ArgoCD reverts it
• Rollbacks are git revert + push

Kustomize for Environment Overlays

# k8s/base/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- deployment.yaml
- service.yaml
images:
- name: registry.example.com/app
  newTag: v1.2.3

# k8s/overlays/production/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
bases:
- ../../base
patches:
- path: replicas-patch.yaml
- path: resources-patch.yaml

Namespace Isolation

# k8s/base/namespace.yaml
apiVersion: v1
kind: Namespace
metadata:
  name: production

---
apiVersion: v1
kind: ResourceQuota
metadata:
  name: prod-quota
  namespace: production
spec:
  hard:
    requests.cpu: "20"
    requests.memory: 40Gi
    limits.cpu: "40"
    limits.memory: 80Gi

---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny
  namespace: production
spec:
  podSelector: {}
  policyTypes:
  - Ingress
  - Egress

Key Takeaways

• Multi-stage Docker builds separate build from runtime — smaller, more secure images
• Always set resource requests and limits — prevent noisy neighbors and OOM kills
• Readiness and liveness probes are essential — without them, you ship broken pods
• HorizontalPodAutoscaler scales based on actual metrics, not guesses
• ArgoCD + GitOps makes deployments auditable, repeatable, and self-healing
• Kustomize handles environment differences without duplicating manifests
• NetworkPolicy is your firewall — deny by default, allow explicitly
• cert-manager automates TLS certificate management with Let's Encrypt

The jump from Docker to Kubernetes is significant, but the payoff is immense: self-healing deployments, automatic scaling, zero-downtime rollouts, and infrastructure as code that you can reason about.