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200-901 Practice Question: An application running on Kubernetes is…
An application running on Kubernetes is experiencing intermittent 503 errors. The logs show 'upstream timed out'. The application is behind a Cisco Application Policy Infrastructure Controller (APIC) load balancer. What is the most likely cause?
⚠ Common exam trap
Cisco often tests the distinction between Readiness and Liveness probes, where candidates mistakenly associate 'upstream timed out' with Liveness probe failures, but the correct focus is on traffic routing via Readiness probes.
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
✓
The Readiness probe is not defined
The 'upstream timed out' error in a Kubernetes environment behind a Cisco APIC load balancer indicates that the load balancer is attempting to forward traffic to a pod that is not ready to accept connections. Without a Readiness probe, Kubernetes assumes the pod is ready as soon as it starts, but the application may still be initializing or unable to handle requests. The APIC load balancer then sends traffic to an unready pod, causing timeouts and 503 errors.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The service port is misconfigured
Why it's wrong here
Service port misconfiguration would cause persistent failure, not intermittent.
- ✓
The Readiness probe is not defined
Why this is correct
Without Readiness probe, the service may send traffic to unready pods causing timeouts.
- ✗
The Liveness probe timeout is too low
Why it's wrong here
Liveness probe affects whether pod is restarted, not load balancer routing.
- ✗
The pod is not ready
Why it's wrong here
Pod not ready is a symptom, not the root cause.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-901 practice question is part of Courseiva's free Cisco 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 200-901 exam.