Google PCA Practice Question: Analyze and optimize technical and business processes
A financial services company runs a high-volume transaction processing system on Google Cloud. They need to ensure that the system can handle sudden spikes in traffic during market open and close. The system uses a managed instance group of Compute Engine VMs behind a load balancer. They want to optimize costs while maintaining performance during peak hours. Which approach should the architect recommend?
⚠ Common exam trap
The trap here is assuming that aggressive cost-saving measures like preemptible VMs or scaling to zero will work for a critical, latency-sensitive system, when a baseline of reliable instances is needed.
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
✓
Use a managed instance group with autoscaling based on CPU utilization, and set a minimum size to handle baseline traffic.
Autoscaling based on CPU utilization with a minimum instance count provides elasticity to handle traffic spikes while ensuring baseline capacity. This allows the system to scale out during market open and close and scale in during quieter periods, optimizing costs without sacrificing performance. Other options either over-provision, use unreliable preemptible VMs, or risk cold starts.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use a managed instance group with autoscaling based on CPU utilization, and set a minimum size to handle baseline traffic.
Why this is correct
Autoscaling based on CPU utilization allows the instance group to add VMs during traffic spikes and remove them when demand drops. Setting a minimum size ensures baseline capacity is always available. This directly addresses both performance during peaks and cost optimization by scaling down during off-peak times.
- ✗
Use preemptible VMs in the managed instance group to reduce compute costs.
Why it's wrong here
Preemptible VMs are much cheaper but can be terminated with little notice, which can cause disruptions during critical trading hours. For a financial transaction system that requires high reliability, preemptible VMs are not suitable. They may reduce costs but at the expense of performance and availability.
- ✗
Use a managed instance group with autoscaling based on a custom metric that tracks queue depth, and set a minimum size of zero.
Why it's wrong here
Autoscaling on queue depth can be effective, but setting a minimum size of zero means no VMs are running during idle periods. When traffic spikes, there will be a cold start delay while VMs boot and initialize, potentially causing performance degradation. For a high-volume transaction system, maintaining a baseline is crucial to handle sudden spikes.
- ✗
Use a managed instance group with a fixed size large enough to handle peak traffic at all times.
Why it's wrong here
A fixed size large enough for peak traffic means you pay for that capacity 24/7, even during off-peak hours. This does not optimize costs, as resources are idle most of the time. While it meets performance requirements, it fails the cost optimization goal.
Go deeper
Related to this question
Learn chapter
Google Cloud Compute Options Overview
Key term
CAN
A CAN (Controller Area Network) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other without a host computer.
Key term
Instance group
An instance group is a collection of virtual machine instances that are managed as a single unit for scaling, load balancing, and lifecycle management in cloud computing.
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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 Google Cloud exam blueprint
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.