A real walkthrough of shrinking bloated Docker images from 1.2GB to 240MB using multi-stage builds, Alpine, and dependency auditing.

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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.

The Problem #

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

Step 1: Multi-Stage Builds #

We split the Dockerfile into build and runtime stages:

dockerfile.dockerfile

# 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.

Step 2: Prune Dev Dependencies #

We added a production-only install in the runtime stage:

dockerfile.dockerfile

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.

Step 3: Audit What's Left #

Running npx depcheck found 12 unused packages. We removed them and dropped another 70MB.

Results #

Metric	Before	After
Image size	1.2GB	240MB
Pull time	38s	8s
Cold start	45s	12s
Registry cost	$180/mo	$40/mo

Best Practices #

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.

How We Cut Our Docker Image Size by 80% and Why It Matters

How We Cut Our Docker Image Size by 80% and Why It Matters

The Problem #

Step 1: Multi-Stage Builds #

Step 2: Prune Dev Dependencies #

Step 3: Audit What's Left #

Results #

Best Practices #

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About Kiril urbonas

How We Cut Our Docker Image Size by 80% and Why It Matters

The Problem#

Step 1: Multi-Stage Builds#

Step 2: Prune Dev Dependencies#

Step 3: Audit What's Left#

Results#

Best Practices#

Stay Updated

Model Fallback Policies for Customer-Facing AI: The Routing Rules That Kept SLA Intact

AWS Cost Audit: 7 Things We Found Wasting Money Every Month

More from DevOps

Incident Postmortems That Actually Prevent Repeat Failures

Artifact Promotion Instead of Rebuilds: The Release Control Pattern That Stopped Drift

Blue-Green Deployment Guardrails in Kubernetes: Lessons from a Failed Friday Rollout

About Kiril urbonas

The Problem #

Step 1: Multi-Stage Builds #

Step 2: Prune Dev Dependencies #

Step 3: Audit What's Left #

Results #

Best Practices #