Kubernetes
Kubernetes (K8s) is an open container-orchestration system. It automates the deployment, scaling, and recovery of containerised applications. If Docker is running a single container, Kubernetes is managing thousands of them.Key conceptsPod — the smallest unit: one or more containers sharing a network namespaceDeployment — describes the desired state (N replicas); K8s maintains it automaticallyService — a stable network address for a set of Pods (in-cluster load balancing)Ingress — HTTP routing from outside the clusterConfigMap / Secret — configuration and secrets decoupled from the imageWhen it makes senseK8s is justified for dozens of microservices or heavy workloads. For a single app — Docker Compose or a managed PaaS (Heroku, Render, Fly.io) is simpler and cheaper.