CKAD Application Observability and Maintenance Practice Question
Which THREE are valid types of probes in Kubernetes?
⚠ Common exam trap
CNCF often tests the distinction between the three official probe types (liveness, readiness, startup) and common but incorrect terms like 'survival' or 'health', which candidates might confuse due to similar-sounding names or general cloud concepts.
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
✓
Startup probe
Startup probes are a valid Kubernetes probe type used to determine when a container application has started successfully. They are particularly useful for legacy applications that have slow startup times, as they delay the start of liveness and readiness probes until the startup probe succeeds, preventing premature container restarts.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Startup probe
Why this is correct
The startup probe is the first probe executed for a container and is designed for applications that require a longer initialization time, such as Java applications or those loading large caches. It runs to completion, and once it succeeds, the kubelet switches to the liveness and readiness probes, allowing the container to be considered ready without being prematurely killed. This prevents the liveness probe from restarting a container that is still starting up.
- ✓
Readiness probe
Why this is correct
The readiness probe determines whether a container is ready to accept traffic, and its result directly controls whether the pod is included in the Service's endpoints. If the readiness probe fails, the pod is removed from the endpoints but the container is not restarted; this is ideal for scenarios where a service depends on downstream resources or data being loaded. Unlike the liveness probe, a failure here does not trigger a restart, only a temporary traffic blackout.
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Liveness probe
Why this is correct
The liveness probe checks if a container is running and healthy, and if it fails, kubelet kills the container and restarts it according to the restart policy. It is intended to detect deadlocks, hangs, or corrupted states where the process is alive but unresponsive, not just whether the process exists. This probe should be used with caution to avoid unnecessary restarts caused by transient failures or during the startup phase.
- ✗
Survival probe
Why it's wrong here
There is no probe type named 'Survival' in Kubernetes; the valid probe types are startup, readiness, and liveness. The term 'survival' is likely a semantic approximation of 'liveness' because both relate to the container staying alive, but it is not a key or identifier recognized by the kubelet. Using 'survival' in a YAML manifest would cause a validation error because it is not a valid handler name.
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Health probe
Why it's wrong here
Kubernetes does not have a probe type called 'Health'; this term may be confused with generic health check patterns in other systems like Azure Load Balancer or cloud health endpoints. In Kubernetes, health is determined by the combination of liveness and readiness probes, and both are configured with specific handlers such as exec, HTTP GET, or TCP socket. A 'health' probe is not part of the Kubernetes API and cannot be used in a pod spec.
Go deeper
Related to this question
Learn chapter
Health Checks: Readiness, Liveness, and Startup Probes
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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