Google PCA Manage and provision cloud infrastructure Practice Question
A company runs a web application on Compute Engine with an HTTP Load Balancer. Users report intermittent 502 Bad Gateway errors. What is the most likely cause?
⚠ Common exam trap
Many exam-takers confuse 502 errors with SSL or quota issues, but the PCA exam specifically tests that 502 errors from an HTTP Load Balancer are almost always due to backend unavailability or overload, not frontend configuration problems.
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
✓
Backend instances are unhealthy or overloaded.
The 502 Bad Gateway error from an HTTP Load Balancer typically indicates that the backend instances are failing to respond to the load balancer's health checks or are overwhelmed, causing the load balancer to consider them unhealthy and return a 502 error. This is the most common cause because the load balancer relies on healthy backends to forward traffic, and overloaded or failing instances cannot handle requests.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Load balancer quota exceeded.
Why it's wrong here
Quota exceeded would prevent creation or scaling, not cause 502 on existing traffic.
- ✗
Firewall rules block health checks.
Why it's wrong here
Blocked health checks would cause the load balancer to consider instances unhealthy, but 502 occurs only when traffic is actually sent to a failing backend.
- ✗
SSL certificate expired.
Why it's wrong here
Expired SSL causes certificate errors, not 502.
- ✓
Backend instances are unhealthy or overloaded.
Why this is correct
502 Bad Gateway typically means the backend is not responding properly.
Go deeper
Related to this question
Learn chapter
Google Cloud Compute Options Overview
Key term
Load balancer
A load balancer is a device or software that distributes incoming network traffic across multiple servers so no single server gets overwhelmed.
Key term
HTTP
HTTP stands for Hypertext Transfer Protocol, the set of rules web browsers and servers use to communicate and transfer web pages over the internet.
About these practice questions
One of 955 original PCA 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 by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCA practice question is part of Courseiva's free Google Cloud 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 PCA exam.