CKAD Application Design and Build Practice Question
A developer wants to create a Job that runs exactly 3 pods in parallel. Which field should be set in the Job spec?
⚠ Common exam trap
It's easy for candidates to confuse `spec.parallelism` with `spec.completions` — candidates often think completions controls concurrency, but it actually defines the total number of successful completions needed, not how many run at once.
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: 3
`spec.parallelism` in a Kubernetes Job spec defines the desired number of Pods that should run concurrently. Setting `spec.parallelism: 3` tells the Job controller to run exactly 3 Pods in parallel, meeting the requirement of running 3 pods simultaneously.
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.ttlSecondsAfterFinished: 3
Why it's wrong here
The ttlSecondsAfterFinished field tells the Kubernetes TTL controller how long to keep a Job around after it completes, after which the Job and its Pods are automatically deleted. It has no effect on scheduling, concurrency, or the number of Pods created while the Job runs. Because it only governs post-completion cleanup, setting it to 3 cannot cause three Pods to be created.
- ✗
spec.backoffLimit: 3
Why it's wrong here
backoffLimit controls how many retries the Job controller will make before it marks the Job as failed; when a Pod fails, the controller waits an increasing backoff period and creates a replacement pod, up to this limit. It is about failure handling and fault tolerance, not the desired number of concurrent Pods. Setting backoffLimit: 3 only permits three failed attempts total, so it does not create three simultaneous Pods.
- ✓
spec.parallelism: 3
Why this is correct
Setting spec.parallelism: 3 tells the Job controller to run up to three Pods concurrently, meaning the Job will schedule three Pods at the same time rather than a single Pod. This field directly controls the degree of parallelism; for a fixed-completion Job, the controller keeps parallelism Pods active until the desired completions count is reached. To achieve exactly three Pods running in parallel, parallelism is the correct knob to use.
- ✗
spec.completions: 3
Why it's wrong here
spec.completions defines how many successful Pod completions are required before the entire Job is considered complete; it is a target count, not a concurrency limit. With completions: 3, the Job controller could still run one Pod at a time if parallelism is left at the default of 1, so it does not ensure three Pods run in parallel. Parallelism, not completions, determines how many Pods run at the same moment.
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