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Best Practices

18. Best Practices

✅ 1. Use Small Base Images

# Use Alpine or slim variants
FROM node:18-alpine        # ~50MB
# instead of
FROM node:18               # ~900MB

# Use distroless for production
FROM gcr.io/distroless/nodejs18-debian11

✅ 2. Leverage Layer Caching

# Bad: copies everything first (cache busted on ANY change)
COPY . .
RUN npm install

# Good: copy package.json first (npm install cached unless deps change)
COPY package*.json ./
RUN npm install
COPY . .

✅ 3. One Process Per Container

# Bad: run Nginx + MongoDB + Redis in one container
# Good: separate containers for each service

docker run -d --name web nginx
docker run -d --name db mongo
docker run -d --name cache redis

✅ 4. Use `.dockerignore`

node_modules
.git
.env
*.log
dist
build
coverage
.DS_Store

✅ 5. Use Specific Tags

# Bad
FROM node:latest

# Good
FROM node:18.17.0-alpine3.18

✅ 6. Set Resource Limits

# Limit CPU and memory to prevent runaway containers
docker run \
  --memory="256m" \
  --cpus="0.5" \
  my-app

✅ 7. Use Health Checks

HEALTHCHECK --interval=30s --timeout=10s --retries=3 \
  CMD curl -f http://localhost:3000/health || exit 1

✅ 8. Keep Secrets Out of Images

# Never do this in Dockerfile:
ENV DB_PASSWORD=mysecret

# Use --env-file or Docker Secrets instead
docker run --env-file .env my-app

✅ 9. Regular Cleanup

# Add to your routine:
docker system prune          # Remove unused resources
docker image prune -a        # Remove all unused images

✅ 10. Use Multi-Stage Builds (Bonus)

# Build stage
FROM node:18 AS builder
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
RUN npm run build

# Production stage (tiny!)
FROM node:18-alpine
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
CMD ["node", "dist/index.js"]