When would you use a Deployment versus a StatefulSet versus a DaemonSet?
What they are really testing: Whether you can match the workload controller to the workload shape. Using a Deployment for a database, or missing DaemonSets for node agents, is a common mistake.
A real interview question
When would you use a Deployment versus a StatefulSet versus a DaemonSet?
What most people say
drag me
“You use a Deployment for most things; StatefulSets and DaemonSets are for special cases.”
It does not say what makes those cases special. The distinction (stable identity/storage for StatefulSet, one-per-node for DaemonSet) is exactly what is being tested.
The follow-ups they ask next
Why does a database need a StatefulSet rather than a Deployment?
Stable network identity and stable per-pod storage: each replica keeps its name and its own volume across restarts, and they start/stop in order, which clustered/stateful systems rely on. A Deployment treats pods as interchangeable and would break that.
How would you run a log-collection agent on every node?
A DaemonSet: it ensures one pod per node and automatically adds the pod when new nodes join, which is exactly what node-level agents need.
What the interviewer is listening for
- Deployment=stateless, StatefulSet=identity+storage, DaemonSet=per-node
- Knows StatefulSet ordering + stable volumes
- Mentions Jobs/CronJobs
What sinks the answer
- Cannot say what makes StatefulSet special
- Would run a DB as a Deployment
- Unaware of DaemonSets for agents
If you genuinely do not know
Say this instead of freezing. Reasoning out loud from what you do know beats silence every single time, and a good interviewer is listening for exactly that.
“Match the controller to the workload: [Deployment for stateless interchangeable replicas (web, APIs)]; [StatefulSet for stable identity + per-pod storage (databases, clustered systems), with ordered startup]; [DaemonSet for one pod per node (log/metrics agents, plugins)]. For run-to-completion work, [a Job or CronJob]. The classic mistake: [a database as a plain Deployment].”
Keep going with kubernetes
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What are the main components of a Kubernetes cluster (control plane and nodes)?
Foundation
What is a Pod, and why do you use a Deployment instead of creating Pods directly?
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What is a Service in Kubernetes, and what are the main types?
Junior
How do you inject configuration and secrets into a pod, and what is the catch with Kubernetes Secrets?
Junior
What is the difference between liveness, readiness, and startup probes?
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