KCNA Kubernetes Fundamentals Practice Question
Which Kubernetes component is responsible for storing the cluster state?
⚠ Common exam trap
CNCF often tests the misconception that kube-apiserver stores the cluster state because it is the central API gateway, but the trap is that kube-apiserver only mediates access while etcd is the actual persistent storage layer.
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 a distributed, consistent key-value store used by Kubernetes to store all cluster data, including configuration, state, and metadata. It is the single source of truth for the cluster; without etcd, the cluster cannot maintain or recover its state. The kube-apiserver is the only component that communicates directly with etcd, but it is etcd itself that physically stores the data.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
kube-scheduler
Why it's wrong here
kube-scheduler only assigns unscheduled pods to nodes by evaluating resource requests, affinity and taints; it holds no cluster state itself. It is tempting because it reads node and pod information constantly, but that data is fetched from the kube-apiserver, which fronts the actual etcd store.
- ✗
kube-apiserver
Why it's wrong here
kube-apiserver exposes the REST interface and validates every request, but the authoritative cluster state lives in etcd, which the API server reads and writes. It is tempting because all state changes pass through it, yet it is a stateless front end rather than the storage layer itself.
- ✓
etcd
Why this is correct
etcd is the distributed key-value store holding all cluster state — objects, configuration and metadata — making it the single source of truth the API server reads and writes, satisfying the requirement to persist cluster state.
- ✗
kube-controller-manager
Why it's wrong here
kube-controller-manager runs reconciliation loops that drive actual cluster state toward the desired state, but it reads and writes that state through the API server rather than holding it. It is tempting because it does persist controller-level data, yet the authoritative store remains etcd behind the kube-apiserver.
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