AZ-900 Describe cloud concepts Practice Question
A company hosts a web application on a single Azure virtual machine. Over the past month, the application's CPU utilization has consistently remained above 90%, causing slow response times. The administrator plans to modify the virtual machine's size from Standard_D2s_v3 (2 vCPUs) to Standard_D8s_v3 (8 vCPUs) to improve performance. Which scaling method does this change represent?
⚠ Common exam trap
Many candidates confuse vertical scaling (changing the size of a single resource) with horizontal scaling (adding more resources), especially when the question describes a performance issue that could be solved by either method, but the specific action of changing the VM size clearly indicates vertical scaling.
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
✓
Vertical scaling (scaling up)
Vertical scaling (scaling up) increases the power of an existing resource by upgrading its size or capacity. In this scenario, changing the virtual machine from Standard_D2s_v3 (2 vCPUs) to Standard_D8s_v3 (8 vCPUs) adds more CPU cores to the same VM, which is a classic example of scaling up. This approach improves performance without adding additional VM instances.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Horizontal scaling (scaling out)
Why it's wrong here
Horizontal scaling involves adding more instances (e.g., increasing the number of VMs), not increasing the capacity of a single instance. This option is incorrect because the administrator is resizing an existing VM, not adding additional VMs.
When this WOULD be correct
An exam scenario where a company adds more virtual machines to a load-balanced set to handle increased traffic, without changing the size of existing VMs, would make horizontal scaling the correct answer.
- ✓
Vertical scaling (scaling up)
Why this is correct
Vertical scaling (or scaling up/down) refers to increasing or decreasing the resources (CPU, memory, etc.) of a single virtual machine or resource. This change increases the CPU capacity of the existing VM, which is a classic example of scaling up.
- ✗
Elastic scaling
Why it's wrong here
Elastic scaling is a characteristic of cloud computing where resources automatically scale in and out based on demand, but it is not a specific method of scaling like vertical or horizontal. The scenario describes a manual change, not an automatic adjustment.
When this WOULD be correct
A scenario where an application automatically adds or removes virtual machines based on CPU utilization thresholds, such as using Azure VM Scale Sets with autoscale rules to handle variable load.
- ✗
Auto-scaling
Why it's wrong here
Auto-scaling is an Azure capability that automatically adjusts capacity based on predefined rules, schedules, or metrics—typically by adding or removing VM instances in a Virtual Machine Scale Set (VMSS). It does not apply here because the administrator is performing a one-time manual resizing action on a single VM, not configuring any automated rule or trigger. In addition, native Azure Autoscale does not vertically resize standard single VMs; it primarily orchestrates horizontal scale-out/in, so calling this action auto-scaling would be incorrect.
When this WOULD be correct
A company hosts a web application on a set of Azure virtual machines behind a load balancer. The application experiences variable traffic, and the administrator configures rules to automatically add or remove VMs based on CPU utilization thresholds. This scenario would make auto-scaling the correct answer.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-900 exam frequently reuses these exact scenarios with slightly different constraints.
✓Vertical scaling (scaling up)Correct answer▾
Why this is correct
Vertical scaling (or scaling up/down) refers to increasing or decreasing the resources (CPU, memory, etc.) of a single virtual machine or resource. This change increases the CPU capacity of the existing VM, which is a classic example of scaling up.
✗Horizontal scaling (scaling out)Wrong answer — click to see why▾
Why this is wrong here
Horizontal scaling (scaling out) involves adding more instances of a resource, such as creating additional virtual machines, not increasing the size of a single VM. The question describes changing the VM size from 2 to 8 vCPUs, which is vertical scaling.
★ When this WOULD be the correct answer
An exam scenario where a company adds more virtual machines to a load-balanced set to handle increased traffic, without changing the size of existing VMs, would make horizontal scaling the correct answer.
Why candidates choose this
Candidates may confuse 'scaling out' with any performance improvement, or think that adding more CPU cores is similar to adding more resources, but horizontal scaling specifically refers to increasing the number of instances.
✗Elastic scalingWrong answer — click to see why▾
Why this is wrong here
Elastic scaling refers to the ability to automatically adjust resources based on demand, often involving both scaling out and scaling in. This question describes a manual, one-time change to a larger VM size, not an automatic adjustment.
★ When this WOULD be the correct answer
A scenario where an application automatically adds or removes virtual machines based on CPU utilization thresholds, such as using Azure VM Scale Sets with autoscale rules to handle variable load.
Why candidates choose this
Candidates may confuse 'elastic scaling' with any scaling action that improves performance, or they may think 'elastic' implies any change in resource capacity.
✗Auto-scalingWrong answer — click to see why▾
Why this is wrong here
Auto-scaling refers to automatically adjusting resources based on demand, not manually changing VM size. The question describes a manual change from Standard_D2s_v3 to Standard_D8s_v3, which is vertical scaling, not auto-scaling.
★ When this WOULD be the correct answer
A company hosts a web application on a set of Azure virtual machines behind a load balancer. The application experiences variable traffic, and the administrator configures rules to automatically add or remove VMs based on CPU utilization thresholds. This scenario would make auto-scaling the correct answer.
Why candidates choose this
Candidates may confuse the concept of scaling (changing resources) with the method of scaling (automatic vs. manual). The term 'auto-scaling' sounds like it could apply to any scaling action, but it specifically requires automated adjustments based on rules.
Analysis generated from the official AZ-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-900 practice question is part of Courseiva's free Microsoft 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 AZ-900 exam.