Kubernetes

What it is: Kubernetes runs containers across a cluster of machines and keeps them in the state you declare: how many replicas, which image, which config.

Core objects: Pods (one or more containers), Deployments (rollouts and replicas), Services (stable networking), ConfigMaps and Secrets, and Namespaces to separate teams.

Why it matters: powerful defaults are not secure defaults. Use RBAC, network policies, non-root pods and Pod Security admission, and remember Secrets are only Base64-encoded unless encryption at rest is on.