Why your image is 1.2 GB

Docker images grow large for three common reasons: a heavy base image, unnecessary files baked into a layer, and build tools that belong in the build stage but end up in production.

The three culprits

A FROM ubuntu base pulls in the entire Ubuntu userland. Most Go or Node apps need a fraction of that. Start from alpine or a distroless image and the base drops from 80MB to under 10MB.

Every COPY . . in your Dockerfile copies your entire build context — including node_modules, .git, test fixtures, and local secrets. A well-tuned .dockerignore is not optional.

DockerfileSalin
# Bad: build tools ship to production
FROM node:20
COPY . .
RUN npm install && npm run build

# Good: two stages, only the artifact moves forward
FROM node:20-alpine AS build
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

FROM nginx:alpine
COPY --from=build /app/dist /usr/share/nginx/html

Layer order matters too: put instructions that change rarely (installing dependencies) before instructions that change often (copying source). Docker’s cache reuses unchanged layers, so a cache miss on COPY . . doesn’t force a reinstall.