CKAD Application Observability and Maintenance Practice Question
What is the purpose of a readiness probe?
⚠ Common exam trap
Test-takers frequently confuse readiness probes with liveness probes, as both are health checks, but readiness probes control traffic routing while liveness probes trigger container restarts.
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
✓
To indicate whether the container is ready to serve traffic
A readiness probe determines whether a container is ready to accept traffic. If the probe fails, the Pod's IP address is removed from the Endpoints of the associated Service, preventing traffic from being routed to an unready container. This is distinct from liveness probes, which restart containers, and startup probes, which indicate successful initialization.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
To restart the container if it becomes unresponsive
Why it's wrong here
This describes the liveness probe, not the readiness probe. While a failing liveness probe triggers the kubelet to kill and restart the container based on the restart policy, a failing readiness probe only stops the pod from receiving traffic. The pod remains running, and the service endpoints controller removes its IP address from backing Services until the probe succeeds again.
- ✓
To indicate whether the container is ready to serve traffic
Why this is correct
A readiness probe tells the kubelet whether the application inside the container is ready to accept incoming requests. When the probe succeeds, the pod is added to the endpoints of Services that select it; when it fails, the pod is removed from those endpoints without being terminated. This prevents clients from sending traffic to pods that are still starting up or are temporarily overloaded.
- ✗
To indicate that the container has started successfully
Why it's wrong here
That is the job of the startup probe, which is used to determine when a container's application has fully initialized. A startup probe is especially useful for containers with slow startup times because it temporarily disables the liveness probe until startup completes. Readiness, by contrast, does not answer 'has it started?' but rather 'is it currently able to serve requests?', and it continues to run after the container is up.
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To measure the resource usage of the container
Why it's wrong here
Probes do not measure resource consumption at all; they only test container health through defined checks such as HTTP endpoints, TCP sockets, or command execution. CPU and memory usage are collected by metrics-server or cAdvisor via kubelet, while resource requests and limits are static fields in the pod specification. A readiness probe has no relationship to resource metering or scheduling decisions.
Go deeper
Related to this question
Learn chapter
Multi-Container Pods and Sidecar Patterns
Key term
Startup Probes
A Kubernetes mechanism that checks whether an application inside a container has started successfully, and delays other health checks until it is ready.
Key term
Readiness Probes
A Kubernetes mechanism that checks if a container is ready to start accepting traffic and serve requests.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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