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Google PCA Practice Question: An e-commerce company is experiencing traffic…
An e-commerce company is experiencing traffic spikes during flash sales. Their application runs on Compute Engine instances behind a TCP load balancer. They want to automatically scale the number of instances based on CPU utilization. Which configuration is required?
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
✓
Create a managed instance group (MIG) with an autoscaling policy based on CPU utilization.
Managed Instance Groups (MIGs) with autoscaling based on CPU utilization is the correct approach. Cloud Functions and Cloud Run are not Compute Engine instance scaling. A global HTTP(S) Load Balancer is not required for TCP traffic.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure Cloud Run for autoscaling and rewrite the application to run in containers.
Why it's wrong here
Cloud Run is a serverless container platform and cannot autoscale Compute Engine instances behind a TCP load balancer; the application would need rewriting and redeployment. It is tempting because Cloud Run does autoscale on request concurrency, which is correct for containerised HTTP services rather than VM-based TCP workloads.
- ✗
Create an unmanaged instance group with a static number of instances and configure Cloud CDN.
Why it's wrong here
An unmanaged instance group holds a fixed instance count, so no autoscaling occurs, and Cloud CDN caches HTTP content rather than scaling Compute Engine capacity on CPU. It tempts when serving static assets, but the requirement is a managed instance group with CPU-based autoscaling.
- ✗
Use Cloud Functions to handle traffic spikes and redirect traffic from the load balancer.
Why it's wrong here
Cloud Functions cannot front a TCP load balancer or scale Compute Engine instances; it runs event-driven code, not traffic redirection. It is tempting for absorbing unpredictable spikes, but that role belongs to a managed instance group with an autoscaler reacting to CPU utilisation.
- ✓
Create a managed instance group (MIG) with an autoscaling policy based on CPU utilization.
Why this is correct
Autoscaling only applies to managed instance groups; a MIG with a CPU utilisation policy adds or removes instances automatically during flash-sale spikes, which an unmanaged group or standalone instances behind the TCP load balancer cannot do.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
Go deeper
Related to this question
Learn chapter
Google Kubernetes Engine (GKE)
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
Cloud Functions
Cloud Functions are serverless compute services that let you run single-purpose code in response to events without managing servers.
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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.