CKAD Application Design and Build Practice Question
A CronJob must run a task every day at midnight, but if the previous job is still running, the new job should be skipped. Which concurrencyPolicy should be set?
⚠ Common exam trap
Watch out — candidates often confuse `Forbid` with `Skip` (which is not a valid Kubernetes value) or incorrectly think `Replace` is the correct way to avoid overlaps, when in fact `Replace` kills the running job instead of skipping the new one.
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
✓
Forbid
B is correct because the `Forbid` concurrency policy ensures that if a previous job instance is still running when the next scheduled trigger fires, the new job is simply skipped. This matches the requirement to avoid overlapping executions without terminating the running job.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Skip
Why it's wrong here
Skip is not a recognized value for the spec.concurrencyPolicy field in a Kubernetes CronJob manifest. The Kubernetes API server validates this field against the allowed enum of Allow, Forbid, or Replace, so any manifest using Skip will be rejected at creation time with a validation error. Although skip sounds like it would match the desired behavior of not launching a new job when the previous one is still running, it cannot be used because it is not a valid concurrency policy.
- ✓
Forbid
Why this is correct
Forbid is the correct concurrencyPolicy because it tells the CronJob controller to skip the scheduled invocation if a job from the previous run is still active. Unlike Allow, it never starts an overlapping job, and unlike Replace, it does not terminate or re-create anything; it simply leaves the current job running and drops that particular tick. This yields the skip-if-still-running behavior that the question asks for.
- ✗
Allow
Why it's wrong here
Allow is the default concurrencyPolicy and permits the CronJob controller to start a new job even when an earlier job from the same CronJob is still running. This means if the task takes longer than 24 hours, a second invocation can begin at the next midnight while the first is still active, violating the requirement to skip overlapping runs. It is therefore the opposite of skipping and is incorrect for this scenario.
- ✗
Replace
Why it's wrong here
Replace does not skip a scheduled run; instead, it terminates the active job from the previous run and immediately starts a new one to cover the current schedule. This is effectively a cancel-and-restart model, which changes the semantics of the task by killing work that may be partially complete rather than simply skipping the next trigger. Because the requirement is to skip an overlapping run without disturbing the existing one, Replace is wrong.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CKAD practice question is part of Courseiva's free CNCF certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CKAD exam.