A real walkthrough of shrinking bloated Docker images from 1.2GB to 240MB using multi-stage builds, Alpine, and dependency auditing.
How We Cut Our Docker Image Size by 80% and Why It Matters
Our main API image had grown to 1.2GB. Deploys were slow, registry costs were climbing, and cold starts on Kubernetes took 45 seconds. Here's exactly how we fixed it.
A quick docker history revealed the culprits:
- Full Node.js 18 base image (900MB layer)
- Dev dependencies included in the final image
- Leftover build artifacts and cache directories
We split the Dockerfile into build and runtime stages:
# Build stage
FROM node:18 AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build
# Runtime stage
FROM node:18-alpine AS runtime
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
COPY package*.json ./
EXPOSE 3000
CMD ["node", "dist/index.js"]
This alone dropped us from 1.2GB to 480MB.
We added a production-only install in the runtime stage:
FROM node:18-alpine AS runtime
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY package*.json ./
RUN npm ci --omit=dev && npm cache clean --force
Down to 310MB.
Running npx depcheck found 12 unused packages. We removed them and dropped another 70MB.
| Metric |
Before |
After |
| Image size |
1.2GB |
240MB |
| Pull time |
38s |
8s |
| Cold start |
45s |
12s |
| Registry cost |
$180/mo |
$40/mo |
- Always use multi-stage builds for compiled or bundled applications
- Use Alpine or distroless base images in production
- Run
npm ci --omit=dev to exclude dev dependencies
- Add a .dockerignore to prevent copying node_modules, .git, and test files
- Audit images quarterly with
docker scout or trivy
Small images mean faster deploys, cheaper storage, and a smaller attack surface. There's no reason to ship your test framework to production.
