Deployments manage desired replicas and revisioned rollout behavior. Availability depends on readiness, capacity and surge or unavailability settings.
Before you start
You should understand Pods, Deployments and Services. Read desired configuration separately from observed cluster state. Use a development cluster when trying changes, and inspect events and status rather than assuming that an accepted manifest means the workload is ready to serve traffic.
The practical goal is to reason through this situation: A new revision becomes ready before old instances are removed under a suitable rollout policy. Read the walkthrough first, then try the interview exercise before opening its answer. The important part is explaining the decision and its consequences, rather than remembering a definition alone.
Step-by-step walkthrough
Step 1: Read rollout policy
Check replica count, surge and permitted unavailability.
Step 2: Inspect readiness and scheduling
A new image is useful only if its Pods can start and serve.
Step 3: Diagnose the blocked boundary
Use events and status before triggering more replacements.
Worked scenario
A new revision becomes ready before old instances are removed under a suitable rollout policy.
A rollout creates new replicas that request more memory than any eligible node offers. Old replicas remain under the availability policy, but the rollout cannot progress. Restarting it repeats the same capacity issue. A different failure, such as a failing readiness probe, needs different evidence and remediation.
Common mistake
A rollout can stall when new Pods cannot schedule or pass readiness.
Verify the behavior
Inspect rollout status, Pod events and probes; verify available capacity for the chosen surge.
Interview exercise
Diagnose a stalled rollout.
Answer and reasoning
Inspect events, replica status, scheduling resources and probe failures before repeatedly restarting the Deployment.
Continue learning
Compare the scenario with the Kubernetes interview questions and test your understanding with the Kubernetes MCQs. For terminology and implementation details, consult the reference material.