kube-apiserver: front end for the Kubernetes control plane. All communication goes through the API server. Validates and processes requests. etcd: key-value store for all cluster data (state, config). The source of truth. Back this up! kube-scheduler: watches for new Pods and assigns them to nodes based on resource requirements, affinity, taints. kube-controller-manager: runs controllers (node controller, replication controller, endpoints, SA/token). cloud-controller-manager: integrates with cloud provider APIs.