What is Docker?
Docker is a containerization platform that packages applications and their dependencies into lightweight, portable containers. Unlike virtual machines that require a full operating system, Docker containers share the host OS kernel while maintaining isolated processes, file systems, and network interfaces.
Containers vs Virtual Machines
Docker Containers
- • Share host OS kernel
- • Lightweight (MBs in size)
- • Fast startup (seconds)
- • Process-level isolation
- • Higher density per host
- • Immutable infrastructure
Virtual Machines
- • Include full OS
- • Heavy (GBs in size)
- • Slow startup (minutes)
- • Hardware-level isolation
- • Lower density per host
- • Complete OS abstraction
Docker Architecture Components
Docker Daemon
Background service managing containers, images, networks, and volumes.
Docker Client
Command-line interface for interacting with Docker daemon via REST API.
Docker Registry
Storage and distribution system for Docker images (Docker Hub, ECR).
Docker Image Layers & Optimization
Layer Caching Strategy
# Optimized Dockerfile FROM node:18-alpine # Copy dependency files first COPY package*.json ./ RUN npm ci --only=production # Copy source code last COPY . . EXPOSE 3000 CMD ["npm", "start"]
Multi-Stage Build
# Build stage FROM node:18 AS builder COPY . . RUN npm ci && npm run build # Production stage FROM node:18-alpine COPY --from=builder /app/dist ./dist COPY package*.json ./ RUN npm ci --only=production CMD ["npm", "start"]
Container Efficiency Calculator
Docker Networking Patterns
Bridge Network (Default)
Containers on the same bridge network can communicate with each other, but are isolated from the host network.
# Create custom bridge network docker network create my-app-network # Run containers on the network docker run -d --network my-app-network --name web nginx docker run -d --network my-app-network --name db postgres
Host Network
Container shares the host's network stack. Best performance but less isolation.
# Run with host networking docker run -d --network host nginx # No port mapping needed curl localhost:80
Volume Management Patterns
Named Volumes
Managed by Docker, persist data beyond container lifecycle.
docker volume create db-data docker run -d -v db-data:/var/lib/postgresql/data postgres
Bind Mounts
Mount host directory into container for development workflows.
docker run -d -v /host/path:/container/path nginx
Real-World Docker Implementations
Netflix
Containerized microservices for their streaming platform.
- • 1000+ microservices in containers
- • Custom base images for security
- • Multi-region container deployment
Shopify
Uses Docker for development environment consistency.
- • Standardized dev environments
- • Ruby application containerization
- • Database migration containers
Goldman Sachs
Adopted Docker for financial trading applications.
- • Low-latency trading systems
- • Regulatory compliance containers
- • Risk management isolation
Spotify
Containerized backend services for music streaming.
- • Music recommendation algorithms
- • Playlist generation services
- • A/B testing infrastructure