Containerization packages an application with all its dependencies into a portable unit. Docker creates containers, and Kubernetes orchestrates them at scale.
What Are Containers
- Lightweight. Share the host OS kernel, unlike VMs
- Portable. Run the same on dev, staging, and production
- Isolated. Each container has its own filesystem and resources
- Fast. Start in seconds, not minutes
Docker Basics
Images and Containers
- Image. A template with the app and its dependencies
- Container. A running instance of an image
- Dockerfile. Instructions to build an image
- Registry. Store and share images (Docker Hub, ECR, GCR)
Key Concepts
- Layers. Images are built in layers, cached for speed
- Volumes. Persistent storage for containers
- Networks. How containers communicate
- Compose. Define multi-container apps in one file
Kubernetes Basics
Kubernetes (K8s) manages containers across multiple machines.
Core Concepts
- Pod. Smallest unit, usually one container
- Deployment. Manages replicas of pods
- Service. Network access to pods
- Ingress. Routes external traffic to services
- ConfigMap/Secret. Configuration and sensitive data
What Kubernetes Does
- Scaling. Automatically scale pods up or down
- Self-healing. Restart failed containers
- Load balancing. Distribute traffic across pods
- Rolling updates. Deploy without downtime
- Resource management. CPU and memory limits
When to Use Containers
- Multiple environments. Consistency from dev to prod
- Microservices. Each service in its own container
- Scaling. Easy to scale individual components
- CI/CD. Build once, deploy anywhere
- Team isolation. Different teams own different containers
When Not to Use Kubernetes
- Single simple app. A monolith on one server is fine
- Small team. K8s has a steep learning curve
- Low traffic. Over-provisioning a simple server is cheaper
- No DevOps expertise. Managed services may be better
Alternatives to Full Kubernetes
- Docker Swarm. Simpler orchestration, built into Docker
- Managed container services. AWS ECS, Google Cloud Run, Azure Container Apps
- Platform as a Service. Heroku, Render, Railway
Getting Started
- Containerize one app. Learn Docker with a real application
- Use Docker Compose. For multi-container local development
- Try a managed service. Cloud Run or ECS before full Kubernetes
- Move to Kubernetes only when needed. When you have multiple services and need orchestration
How Switch 2 One Helps
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