# Multi-Stage Docker Builds

## Basic Multi-Stage Pattern

```dockerfile
# Build stage
FROM node:18-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production

# Production stage
FROM node:18-alpine AS production
WORKDIR /app
COPY --from=builder /app/node_modules ./node_modules
COPY . .
EXPOSE 3000
CMD ["npm", "start"]
```

## Python with Virtual Environment

```dockerfile
# Build stage
FROM python:3.11-slim AS builder
WORKDIR /app
COPY requirements.txt .
RUN python -m venv /opt/venv
ENV PATH="/opt/venv/bin:$PATH"
RUN pip install --no-cache-dir -r requirements.txt

# Production stage
FROM python:3.11-slim AS production
WORKDIR /app
COPY --from=builder /opt/venv /opt/venv
ENV PATH="/opt/venv/bin:$PATH"
COPY . .
CMD ["python", "app.py"]
```

## Benefits
- Smaller final image size
- Separation of build and runtime dependencies  
- Better caching strategies
- Security (no build tools in production image)

## Best Practices
- Use specific base image versions
- Copy only necessary files to production stage
- Run as non-root user in production stage
- Use .dockerignore to exclude unnecessary files