CV0-004 Troubleshooting Practice Question
A cloud application returns HTTP 503 errors during high traffic. The application runs on VMs behind a load balancer. Which action is most likely to resolve the issue?
⚠ Common exam trap
CV0-004 often tests whether candidates confuse DNS or health-check tuning with actual capacity scaling — the trap is picking a 'quick fix' like restarting a server instead of addressing the root cause of insufficient backend capacity.
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
✓
Add additional VMs to the backend pool.
HTTP 503 Service Unavailable during high traffic indicates that the backend servers cannot handle the current load, often because all VMs are saturated or the load balancer has no healthy backends. Adding additional VMs to the backend pool increases capacity and distributes the load, directly addressing the root cause. This is the standard horizontal scaling response to traffic-induced 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.
- ✗
Restart the web server service on one VM.
Why it's wrong here
Restarting one VM's web service does not add capacity, so the remaining VMs stay saturated and 503s persist. It tempts because service restarts clear stuck worker processes, which is the right fix when a single VM hangs rather than when load exceeds the pool's total capacity.
- ✗
Change the DNS TTL to a lower value.
Why it's wrong here
DNS TTL controls how long resolvers cache records; it does not add backend capacity, so 503s from saturated VMs continue. It tempts because low TTLs speed failover during migrations or unhealthy-endpoint changes, which is the correct scenario for this setting, not traffic-driven overload.
- ✗
Increase the health check interval on the load balancer.
Why it's wrong here
Lengthening the health check interval delays detection of unhealthy VMs, so the load balancer keeps routing traffic to failed nodes and 503s worsen. It tempts because longer intervals reduce probe overhead, which suits stable, low-traffic environments, but under high traffic it removes the balancer's ability to react.
- ✓
Add additional VMs to the backend pool.
Why this is correct
HTTP 503 signals backend capacity exhaustion, so the load balancer has healthy targets but insufficient compute. Adding VMs to the backend pool increases aggregate capacity to absorb the traffic spike, directly addressing the overload causing the errors.
Visual reference
Go deeper
Related to this question
About these practice questions
One of 834 original CV0-004 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
This CV0-004 practice question is part of Courseiva's free CompTIA 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 CV0-004 exam.