Your Docker Images Are Bigger Than They Need to Be

Why Image Size Matters

Large Docker images significantly impede development velocity and increase operational costs. A 1.2GB image can take approximately 8 minutes to push to a registry, while an optimized 120MB image takes only 45 seconds – a 10-minute savings per deploy, potentially costing teams 50 minutes per day for frequent deployments.

Key Insights

• 10x Reduction: Optimizing a Node.js project reduced image size from 1.2GB to 120MB.
• Layer Caching: Copying package.json before other files leverages Docker’s layer caching for faster builds.
• Distroless Images: Google’s distroless images minimize image size and attack surface by excluding unnecessary tools.

Working Example

# Optimized Dockerfile (Node.js Example)
FROM node:18-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production && \
npm cache clean --force
FROM node:18-alpine
WORKDIR /app
RUN addgroup -g 1001 -S nodejs && \
adduser -S nodejs -u 1001
COPY --from=builder /app/node_modules ./node_modules
COPY --from=builder /app .
USER nodejs
EXPOSE 3000
CMD ["node", "server.js"]

Practical Applications

• Stripe/Coinbase: Utilize multi-stage builds and minimal base images for faster deployments and reduced infrastructure costs.
• Large Monoliths: Avoid including development dependencies and unnecessary tools in production images to minimize the attack surface and improve security.

References:

• https://dev.to/polliog/your-docker-images-are-bigger-than-they-need-to-be-2ca