CKAD Application Observability and Maintenance Practice Question
You have a Deployment running a web server that takes 30 seconds to initialize. You want to ensure that the load balancer does not send traffic to the pod until it is ready. Which probe should you configure?
⚠ Common exam trap
Many exam-takers confuse Startup probes with Readiness probes, thinking a Startup probe alone will gate traffic, but only the Readiness probe controls whether the Service routes traffic to the Pod.
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
✓
Readiness probe
A Readiness probe is the correct choice because it determines whether a Pod is ready to serve traffic. In this scenario, the web server takes 30 seconds to initialize, so a Readiness probe (e.g., an HTTP GET on the application's health endpoint) will prevent the Service (and thus the load balancer) from sending requests until the probe succeeds, ensuring zero traffic is routed to an uninitialized Pod.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Readiness probe
Why this is correct
The readiness probe is the correct mechanism because it directly controls whether a pod is added to or removed from the endpoints of a Service. When the probe fails, the kubelet marks the pod as NotReady, and the endpoints controller immediately removes its IP from all backing Services, stopping new traffic. This is essential for deployments where the application needs time to warm up or load data before accepting requests, and it also enables zero-downtime rolling updates by holding back new pods until they are fully operational.
- ✗
Resource limit
Why it's wrong here
Resource limits define the maximum CPU and memory a container can consume, enforced by the kubelet and the container runtime. They influence scheduling decisions, OOM killer behavior, and throttling, but they have no interaction with the Service's endpoints list or the pod readiness state. A pod exceeding its memory limit may be terminated, but that is a restart/kill action, not a traffic routing action, so it cannot serve as a substitute for a readiness probe.
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Startup probe
Why it's wrong here
Startup probes are designed for containers that need extra time to initialize, such as those loading large models or establishing database connections; they run only once and, once successful, stop. However, a successful startup probe merely signals that the container has booted far enough for other probes (liveness and readiness) to take over; it does not itself influence whether the pod receives traffic after startup. For controlling Service routing continuously, a readiness probe is required because it provides an ongoing indication of whether the application can serve requests.
- ✗
Liveness probe
Why it's wrong here
Liveness probes check whether a container is still running and healthy; if they fail, the kubelet kills and restarts the container according to the restart policy. Crucially, a failing liveness probe does not remove the pod from Service endpoints—the pod continues to receive traffic until the restart actually happens, which could expose users to errors. While liveness probes help self-heal broken containers, they are not a traffic-routing mechanism and cannot replace a readiness probe for determining Service membership.
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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.