Multi-Stage Builds & Image Optimization

1. The Anti-Pattern: Single-Stage Image Bloat

When building applications in a single stage, all build tooling remains permanently frozen in the production image layers:

2. Base Image Spectrum: From Ubuntu to Scratch

Selecting the right runtime base image dictates performance, memory footprint, and security posture:

3. Production Statically Compiled Go / Rust Service (10 MB Image)

Compile your backend code inside a heavyweight Golang builder stage, and copy only the compiled binary into an empty scratch image:

# ---------------------------------------------
# STAGE 1: Compilation Environment (Heavy: ~800 MB)
# ---------------------------------------------
FROM golang:1.22-alpine AS builder

WORKDIR /src

# Cache dependencies
COPY go.mod go.sum ./
RUN go mod download

# Copy source code and build statically linked CGO-disabled binary
COPY . .
RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags="-s -w" -o /bin/api-server .

# ---------------------------------------------
# STAGE 2: Minimal Zero-Overhead Production (Tiny: ~12 MB)
# ---------------------------------------------
FROM scratch

# Copy SSL root certificates for outbound HTTPS calls
COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/

# Copy only the compiled binary
COPY --from=builder /bin/api-server /bin/api-server

# Expose service port and set entrypoint
EXPOSE 8080
ENTRYPOINT ["/bin/api-server"]

4. Production Next.js Standalone Multi-Stage Build

By enabling output: 'standalone' in next.config.js, Next.js automatically traces your imports and copies only required node_modules into a minimal bundle:

# Stage 1: Install all dependencies (including devDependencies for build)
FROM node:20-alpine AS deps
RUN apk add --no-cache libc6-compat
WORKDIR /app
COPY package.json package-lock.json ./
RUN npm ci

# Stage 2: Build Next.js application
FROM node:20-alpine AS builder
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY . .
ENV NEXT_TELEMETRY_DISABLED=1
RUN npm run build

# Stage 3: Minimal Production Runner Stage
FROM node:20-alpine AS runner
WORKDIR /app
ENV NODE_ENV=production
ENV PORT=3000

# Create dedicated unprivileged runtime user
RUN addgroup --system --gid 1001 nodejs && adduser --system --uid 1001 nextjs

# Copy static assets and traced standalone bundle
COPY --from=builder /app/public ./public
COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./
COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static

USER nextjs
EXPOSE 3000
CMD ["node", "server.js"]