Docker Image Optimization: Smaller, Secure and Faster Builds

1. Use official minimal base images

Start from alpine or distroless where appropriate. Avoid including build tools in runtime images.

2. Multi-stage builds

# builder stage
FROM node:18-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build
# runtime
[...]

3. Layer caching and buildkit

Order Dockerfile steps to maximize cache reuse and enable BuildKit for faster incremental builds.

4. Remove unnecessary files and use .dockerignore

Exclude test artifacts, docs and node_modules (when building elsewhere) from context.

5. Scan images and lock dependencies

Use tools like Trivy and anchor to scan; pin base images and use immutable tags.

6. Minimize layers and combine RUNs

Combine apt installs and clean caches in one RUN to avoid extra layers.

7. Reproducible builds

Use lockfiles and deterministic build steps to ensure identical images across environments.