CKA Workloads and Scheduling Practice Question
You have a CronJob that runs a batch job every 5 minutes. The job takes about 2 minutes to complete. However, if a job takes longer than 5 minutes, you want to prevent a new job from starting until the previous one finishes. Which CronJob field should you configure?
⚠ Common exam trap
Many candidates confuse `concurrencyPolicy` with `suspend` or `startingDeadlineSeconds`, mistakenly thinking pausing or delaying the job will solve the overlap issue, when only `Forbid` explicitly prevents concurrent runs.
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
✓
concurrencyPolicy: Forbid
The `concurrencyPolicy` field in a CronJob spec controls how the controller handles overlapping job executions. Setting it to `Forbid` ensures that if a previous job is still running when the next scheduled time arrives, the new job is skipped, preventing concurrent runs. This directly addresses the requirement to block a new job from starting until the previous one finishes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
successfulJobsHistoryLimit
Why it's wrong here
This field specifies the number of successfully completed jobs that Kubernetes retains in the system's history for auditing and debugging. Adjusting this limit only cleans up old metadata and pods; it has no impact on active job scheduling or preventing concurrent executions.
- ✓
concurrencyPolicy: Forbid
Why this is correct
Setting `concurrencyPolicy: Forbid` ensures that if a scheduled job is still running when the next interval arrives, the CronJob controller skips the new execution. This guarantees that only one instance of the batch job runs at any given time, preventing overlapping executions.
- ✗
suspend: true
Why it's wrong here
Enabling the `suspend` field pauses the CronJob entirely, preventing any future jobs from being scheduled until it is set back to false. While this stops concurrent runs, it does so by completely halting the 5-minute batch processing schedule.
- ✗
startingDeadlineSeconds
Why it's wrong here
This parameter defines the maximum duration in seconds that a job can start late if it misses its scheduled time due to controller delays or resource constraints. It does not manage concurrency or prevent multiple instances from running concurrently if they start on time.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CKA 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 CKA exam.