Kubernetes stores its cluster state (API objects) in etcd, making A correct. etcd is a distributed, strongly consistent key-value store that serves as the source of truth for the Kubernetes control plane. When you create or update objects such as Pods, Deployments, ConfigMaps, Secrets, or Nodes, the kube-apiserver validates the request and then persists the desired state into etcd. Controllers and the scheduler watch the API for changes (which ultimately reflect etcd state) and reconcile the cluster to match that desired state.
etcd’s consistency guarantees are crucial. Kubernetes relies on accurate, up-to-date state to make scheduling decisions, enforce RBAC/admission policies, coordinate leader elections, and ensure controllers behave correctly. etcd uses the Raft consensus algorithm to replicate data among members and requires quorum for writes, enabling fault tolerance when deployed in HA configurations (commonly three or five members).
The other options are incorrect in Kubernetes’ standard architecture. ZooKeeper is a distributed coordination system used by some other platforms, but Kubernetes does not use it as its primary datastore. Redis is an in-memory data store used for caching or messaging, not as Kubernetes’ authoritative state store. “ControlPlaneStore” is not a standard Kubernetes component.
Operationally, etcd health is one of the most important determinants of cluster reliability. Slow disk I/O or unstable networking can degrade etcd performance and cause API latency spikes. Backup and restore procedures for etcd are critical disaster-recovery practices, and securing etcd (TLS, access restrictions) is essential because it may contain sensitive data (e.g., Secrets—often base64-encoded, and optionally encrypted at rest depending on configuration).
Therefore, the verified Kubernetes datastore is etcd, option A.
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