CKA Practice Question: Cluster Architecture, Installation and Configuration
Which control plane component is responsible for storing the cluster state and configuration?
⚠ Common exam trap
It's easy for candidates to confuse the kube-apiserver as the storage component because it is the primary interface for all cluster operations, but it is actually a stateless API gateway that relies entirely on etcd for persistence.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
etcd
etcd is the distributed key-value store that serves as the single source of truth for the entire cluster, storing all cluster state data such as configurations, secrets, service endpoints, and resource specifications. The kube-apiserver reads from and writes to etcd exclusively, making it the only component that directly persists the cluster's desired and current state.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
etcd
Why this is correct
etcd is a distributed, consistent, and highly available key-value store that serves as Kubernetes' backing store for all cluster data. It persistently stores the entire cluster state, including configuration data, metadata for all Kubernetes objects like Pods, Deployments, and Services, and the desired state of the system. Its robust consistency model is critical for ensuring that all control plane components operate on a single, unified source of truth.
- ✗
kube-controller-manager
Why it's wrong here
The kube-controller-manager runs controller processes that regulate cluster behaviour, such as node health and replica scaling, but it does not persist any data; it reads and writes cluster state from the correct component, etcd. It is tempting because controllers manage desired state, yet the stem asks for the storage location of that state, not the logic that enforces it. The kube-controller-manager would be correct if the question concerned which component reconciles actual state with desired state.
- ✗
kube-apiserver
Why it's wrong here
The kube-apiserver acts as the front-end for the Kubernetes control plane, exposing the Kubernetes API and serving as the primary interface for all cluster interactions. While it processes, validates, and serves API requests, it does not store any persistent cluster data itself. Instead, the API server is responsible for communicating with etcd to read and write the cluster's state, effectively acting as a stateless gateway to the persistent data store.
- ✗
kube-scheduler
Why it's wrong here
The kube-scheduler is a control plane component responsible for watching for newly created Pods that have no assigned node and selecting an appropriate node for them to run on. It makes scheduling decisions based on various factors, including resource requirements, policy constraints, taints/tolerations, and affinity/anti-affinity rules. However, the scheduler does not store any cluster state; it merely updates the Pod's `nodeName` field via the API server, which then persists this change in etcd.
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