### arch

```{eval-rst}
.. plantuml::

   @startuml
   ' top to bottom direction
   ' left to right direction
   skinparam rectangleStyle rounded
   skinparam shadowing false
   skinparam arrowColor #2E86C1
   skinparam packageStyle rectangle
   skinparam defaultTextAlignment center
   
   title Kubernetes Architecture (Vertical Layout)
   
   ' =============================
   ' TOP: CLIENTS
   ' =============================
   rectangle "kubectl / API Clients" as kubectl #lightgray
   
   ' =============================
   ' MIDDLE: CONTROL PLANE
   ' =============================
   rectangle "kube-apiserver\n(entrypoint)" as apiserver #lightblue
   
   rectangle "kube-controller-manager\n(reconciliation loop)" as controller #white
   rectangle "kube-scheduler\n(pod placement)" as scheduler #white
   rectangle "etcd\n(cluster state)" as etcd #white
   
   ' Stack control-plane visually
   apiserver -down-> controller
   apiserver -down-> scheduler
   apiserver -down-> etcd
   
   ' Client to API Server
   kubectl -down-> apiserver : REST API
   
   ' =============================
   ' BOTTOM: WORKER NODES
   ' =============================
   package "Worker Node(s)" as nodes {
       top to bottom direction
       rectangle "kubelet\n(node agent)" as kubelet #lightyellow
       rectangle "container runtime\n(containerd / CRI-O)" as runtime #white
       rectangle "Pods (Workloads)" as pods #white
       rectangle "kube-proxy\n(service networking)" as kubeproxy #white
       rectangle "CNI Plugin\n(Calico / Cilium / etc.)" as cni #white
   }
   
   ' Control-plane to worker node
   apiserver -down--> kubelet
   
   ' Inside node
   kubelet -down-> runtime
   runtime -down-> pods
   
   ' Network components
   kubeproxy -right-> pods
   cni -left-> pods
   
   @enduml