Blue Environment (Current)  →  Switch traffic  →  Green Environment (New)

Production (100%) → Canary (5%) → Expand (50%) → Full (100%)

Instance 1 → Instance 2 → Instance 3 → Instance 4

if (featureFlags.isEnabled('new-checkout')) {
  return <NewCheckout />
} else {
  return <LegacyCheckout />
}

# GitHub Actions example
name: CI
on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Install dependencies
        run: pnpm install
      - name: Run tests
        run: pnpm test
      - name: Run linter
        run: pnpm lint

deploy:
  needs: test
  runs-on: ubuntu-latest
  if: github.ref == 'refs/heads/main'
  steps:
    - name: Deploy to production
      run: ./deploy.sh

resource "aws_instance" "web" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
  
  tags = {
    Name = "WebServer"
    Environment = "production"
  }
}

version: '3.8'
services:
  web:
    build: .
    ports:
      - "3000:3000"
    environment:
      - NODE_ENV=production
  db:
    image: postgres:14
    volumes:
      - db-data:/var/lib/postgresql/data

volumes:
  db-data:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: web
        image: myapp:latest
        ports:
        - containerPort: 3000

app.get('/health', (req, res) => {
  res.status(200).json({
    status: 'healthy',
    timestamp: new Date().toISOString(),
    version: process.env.APP_VERSION
  })
})