CKAD Application Design and Build Practice Question
A Job must run exactly 3 Pods in parallel. Which Job manifest field achieves this?
⚠ Common exam trap
A common mistake in the CKAD exam is confusing `.spec.parallelism` (the number of Pods to run concurrently) with `.spec.completions` (the total number of successful Pods required to complete the Job). Candidates often select `.spec.completions` thinking it controls parallelism.
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
✓
.spec.parallelism
`.spec.parallelism` in a Kubernetes Job manifest specifies the maximum number of Pods that should run concurrently. Setting this field to 3 ensures exactly 3 Pods run in parallel, as required by the question.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
.spec.activeDeadlineSeconds
Why it's wrong here
The .spec.activeDeadlineSeconds field sets a maximum duration for the entire Job's lifetime. When this deadline expires, the Job is terminated and marked as failed, regardless of which Pods are still running. It does not influence how many Pods are scheduled concurrently; it is purely a timeout for the whole Job execution. So it cannot be used to specify running three Pods in parallel.
- ✗
.spec.completions
Why it's wrong here
The .spec.completions field specifies the total number of Pods that must finish successfully before the Job is considered complete. It tracks cumulative successful completions rather than how many Pods are running at once. For instance, setting completions to 3 would require three successful Pods overall, but they could run sequentially or in parallel depending on the parallelism field. Thus, completions controls the desired outcome count, not the degree of concurrency.
- ✓
.spec.parallelism
Why this is correct
The .spec.parallelism field is the correct way to control how many Pods run concurrently. Setting parallelism to 3 instructs the Job controller to launch three Pods simultaneously, ensuring the Job runs exactly three Pods in parallel. It directly defines the maximum number of active Pods at any moment, independent of the total completion count. If completions is also set, parallelism determines how many of the total completions are processed at a time.
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.spec.backoffLimit
Why it's wrong here
The .spec.backoffLimit field controls the number of retries the Job controller will perform after a Pod fails before marking the Job as failed. This is a failure-handling mechanism that determines how many times a Pod's failure can be retried, not how many Pods should be launched in parallel. Setting backoffLimit has no effect on concurrency; it only governs the tolerance for Pod failures. Therefore, it cannot be used to achieve three running Pods.
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