CKAD Application Design and Build Practice Question
Which of the following are valid concurrencyPolicy values for a CronJob? (Select all that apply.)
⚠ Common exam trap
The CKAD exam expects you to know all three valid values for concurrencyPolicy. Do not mistakenly think that Replace is invalid; it is one of the three accepted values. Also, avoid selecting Parallel or Serial, as they are not part of the Kubernetes API.
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
✓
Replace
Within a Kubernetes CronJob, the concurrencyPolicy field accepts three valid values: Allow, Forbid, and Replace. Allow permits multiple concurrent executions of the same job. Forbid prevents new executions while a previous one is still running. Replace cancels the currently running job and starts a new one in its place. Options C (Parallel) and E (Serial) are not valid values. Therefore, the correct answers are Replace, Allow, and Forbid.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Replace
Why this is correct
The `Replace` policy is a valid concurrencyPolicy value, but it is not one of the two selected as correct in this question. It terminates the currently running job and starts a new one when the next scheduled time arrives.
- ✓
Allow
Why this is correct
The `Allow` policy is the default `concurrencyPolicy` and permits a new job to be created even if a previously scheduled job is still running. This means multiple job Pods from the same CronJob can overlap, which is useful for workloads that are safe to run concurrently. However, you must ensure your application can handle parallel instances.
- ✗
Parallel
Why it's wrong here
`Parallel` is not a recognized value for `concurrencyPolicy` in the CronJob API. The valid values are only `Allow`, `Forbid`, and `Replace`; the API server rejects any other string as an invalid enum value. If you need multiple CronJob-created jobs to run simultaneously, the correct policy is `Allow`, not `Parallel`.
- ✓
Forbid
Why this is correct
The `Forbid` policy ensures that if the job from the previous schedule is still active, the CronJob controller skips the new scheduled run. This prevents overlapping executions and is ideal for batch jobs that must process sequentially. Note that the missed run is not queued or retried later; it is simply dropped until the next schedule.
- ✗
Serial
Why it's wrong here
`Serial` is another invalid value for the `concurrencyPolicy` field. Although it sounds like a policy that would queue jobs one after another, Kubernetes does not implement a serial queue; instead, `Forbid` is used to prevent overlapping runs. Using `Serial` in a CronJob manifest will cause a validation error from the Kubernetes API server.
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JA
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.