Google ACE Practice Question: A company's application currently runs on a…

A company's application currently runs on a single Compute Engine VM with a persistent disk. The application serves read-heavy traffic and the single VM is becoming a bottleneck. The application is stateless. Which change provides the most immediate horizontal scalability improvement?

⚠ Common exam trap

Many exam-takers confuse vertical scaling (Option A) with horizontal scaling, or think that adding more disks (Option C) or enabling live migration (Option D) can solve a compute bottleneck, when only distributing the load across multiple instances (Option B) provides true horizontal scalability.

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 from the VM and configure autoscaling with a load balancer.

Creating a Managed Instance Group (MIG) from the existing VM and configuring autoscaling with a load balancer directly addresses the read-heavy, stateless bottleneck by distributing traffic across multiple VM instances. This provides immediate horizontal scalability, as new instances are automatically provisioned or terminated based on load, without requiring any application changes.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
Upgrade the existing VM to a larger machine type (vertical scaling).
Why it's wrong here
Resizing the existing VM to a larger machine type (vertical scaling) does increase CPU and memory, but it requires stopping the instance, causing downtime during the resize. It also hits a hard upper bound based on the largest machine type available in that zone or region, and the single VM remains a single point of failure. For sustained or unpredictable spikes, this approach cannot elastically scale down and costs more than needed.
✓
Create a Managed Instance Group from the VM and configure autoscaling with a load balancer.
Why this is correct
A Managed Instance Group (MIG) built from the VM, combined with an HTTP(S) load balancer, delivers horizontal scaling by launching additional identical VM instances on demand. The autoscaler monitors metrics like CPU utilization or request rate and adjusts instance count, while the load balancer distributes traffic evenly and performs health checks. This approach is elastic, fault-tolerant, and the standard pattern for stateless, scalable web workloads.
✗
Add more persistent disks to the existing VM to handle more I/O.
Why it's wrong here
Adding more persistent disks increases available storage capacity and aggregate I/O throughput for the VM, which can help if the workload were storage-bound. However, the stated bottleneck is a single VM's inability to handle more incoming requests or compute load — persistent disks do not add vCPUs, memory, or network endpoints. With only one VM, extra disks are still accessed through the same single instance's CPU/memory and network stack.
✗
Enable live migration on the existing VM so it can move between hosts.
Why it's wrong here
Live migration is a Google Compute Engine feature that transparently moves a running VM to a different physical host to perform maintenance, typically without downtime. It does not alter the VM's resource capacity, network bandwidth, or request-handling ability, and it cannot be used to distribute load across multiple machines. Thus, it has no effect on the scenario's need to handle increased traffic.

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Google ACE Practice Question: A company's application currently runs on a…

Why each option matters

Option-by-option breakdown

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