KCNA Kubernetes Fundamentals Practice Question
You have a Deployment named 'web-app' that manages 3 replicas. You need to update the container image from version 1.0 to 2.0 with zero downtime. Which Kubernetes feature is designed to handle this automatically when you update the Deployment's pod template?
⚠ Common exam trap
A common mix-up: candidates confuse the Deployment's automatic rolling update with manual update methods (like onDelete) or think that a ReplicationController or DaemonSet can handle zero-downtime updates in the same way, but only the Deployment's RollingUpdate strategy provides this out-of-the-box behavior for stateless applications.
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
✓
Rolling update strategy in the Deployment
A Deployment's default update strategy is 'RollingUpdate', which automatically replaces old Pods with new ones in a controlled manner, ensuring zero downtime by incrementally scaling down old replicas and scaling up new replicas. When you update the container image in the Deployment's pod template, Kubernetes triggers a rolling update that maintains the desired number of replicas throughout the process.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
ReplicationController
Why it's wrong here
A ReplicationController maintains a fixed pod count but lacks the Deployment's rolling-update and revision-history mechanics, so changing its template does not orchestrate a zero-downtime image change. It is tempting as the original replication primitive, and would be correct for simple, static replica maintenance without updates.
- ✓
Rolling update strategy in the Deployment
Why this is correct
Rolling updates replace pods incrementally, respecting maxSurge and maxUnavailable, so the Deployment keeps serving traffic throughout the image change from 1.0 to 2.0. This satisfies the zero-downtime constraint directly, since Kubernetes creates new pods before terminating old ones rather than recreating all three at once.
- ✗
DaemonSet
Why it's wrong here
A DaemonSet places one pod on every node for node-level agents, so it does not manage the three replicated pods or roll out a new image. It is tempting because DaemonSets do perform rolling updates of their own pods, and would be correct for deploying log or monitoring agents cluster-wide.
- ✗
StatefulSet's onDelete strategy
Why it's wrong here
StatefulSet's onDelete strategy updates pods only when manually deleted, so it cannot deliver automatic zero-downtime rollout of a new image. It is tempting because StatefulSets do support rolling updates, and would be correct for ordered, stable-identity workloads such as databases.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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