CKAD Application Design and Build Practice Question
A Pod with an init container and a main container is created. The init container runs a script that takes 10 seconds. The main container's startupProbe has initialDelaySeconds: 5. When does the startupProbe begin?
⚠ Common exam trap
The trap here is that candidates mistakenly think probes start counting from Pod creation time, ignoring the sequential blocking nature of init containers, which must complete before any main container probes are scheduled.
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
✓
After the init container completes, then plus 5 seconds
The startupProbe does not begin until the Pod's containers are actually running. Init containers must complete successfully before any main containers start. Therefore, the startupProbe's initialDelaySeconds of 5 is counted from the moment the main container starts, which is after the init container finishes its 10-second script. The probe begins 5 seconds after the main container starts, not from Pod creation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
5 seconds after the pod is created
Why it's wrong here
This option assumes the startupProbe's initialDelaySeconds counts from pod creation, but the clock only starts once the main container transitions to Running. Before that, the init container must execute and finish; until it does, the main container isn't even started, so no probe can be active. Thus at 5 seconds post-creation, the probe almost certainly has not begun, as the init phase may still be running.
- ✗
10 seconds after the pod is created
Why it's wrong here
Choosing a fixed 10-second mark ignores both the requirement that the init container complete first and the fact that initialDelaySeconds is relative to the main container's start time, not to pod creation. The actual probe start time is entirely dependent on how long the init container runs—if it takes 20 seconds, the probe would start at 25 seconds. A hard-coded 10 seconds fails to account for the dynamic init duration and the configured delay.
- ✗
Immediately after the pod is created
Why it's wrong here
A startupProbe is only executed by the kubelet on a container that is already running, and the main container cannot run until every init container in the pod has completed successfully. Pod creation merely schedules the init sequence; the main container's start is blocked during that time. Therefore, the probe cannot fire immediately because the main container hasn't been created or started yet.
- ✓
After the init container completes, then plus 5 seconds
Why this is correct
The startupProbe begins only after the main container has entered the Running state, which is possible only after all init containers complete successfully. At that point, the kubelet waits the configured initialDelaySeconds—here, 5 seconds—before performing the first probe. Hence the first probe occurs at the init container's total runtime plus 5 seconds, not at pod creation plus 5 seconds.
Go deeper
Related to this question
About these practice questions
Courseiva writes every CKAD question from scratch — 826 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
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.