Containerization

Containerization packages an application and all its dependencies (libraries, runtime, config files) into a standardized unit called a container. Unlike virtual machines, containers share the host OS kernel, making them lightweight and fast to start.

Docker is the most popular containerization platform. A Dockerfile defines the container image — the base OS, dependencies to install, files to copy, and the command to run. Images are stored in registries (Docker Hub, GitHub Container Registry, AWS ECR).

Key benefits include environment consistency ("works on my machine" → works everywhere), isolation (each container is independent), portability (run anywhere Docker is installed), and efficient resource usage (containers are much lighter than VMs).

Docker Compose manages multi-container applications locally (e.g., app + database + cache). For production, container orchestration platforms like Kubernetes handle scaling, networking, health checks, and rolling deployments across clusters.