AZ-900 Describe cloud concepts Practice Question
An IT team manages a customer relationship management (CRM) application hosted on a single Azure virtual machine. As the number of users grows, the CPU and memory usage on the VM consistently exceed 90%. The team decides to increase the VM size from Standard_D2s_v3 (2 vCPUs, 8 GB RAM) to Standard_D8s_v3 (8 vCPUs, 32 GB RAM) to handle the increased load. The application is not designed to run on multiple servers simultaneously. This approach represents which type of scaling in the cloud?
⚠ Common exam trap
Watch out — candidates often confuse vertical scaling with auto-scaling, but auto-scaling is an automated process that can scale either vertically or horizontally based on rules, whereas this question describes a manual, one-time resizing without any automation.
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
Increasing the VM size from Standard_D2s_v3 to Standard_D8s_v3 adds more vCPUs and RAM to the same virtual machine, which is the definition of vertical scaling (scaling up). This approach is appropriate because the application cannot run on multiple servers simultaneously, so adding resources to the existing single VM is the only viable option to handle the increased load.
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
Why it's wrong here
Horizontal scaling (scaling out) involves adding more instances of the same resource, such as deploying additional virtual machines. In this scenario, the team is increasing the capacity of the existing single VM, not adding more VMs.
When this WOULD be correct
This option would be correct in a scenario where an application is designed to run across multiple servers (e.g., a web app with a load balancer) and the team adds more VMs to handle increased traffic, such as adding two more VMs to a web server farm.
- ✓
Vertical scaling
Why this is correct
Vertical scaling, also known as scaling up, increases the capacity of a single resource by upgrading its specifications, such as moving a virtual machine to a larger SKU with more vCPUs and RAM. In this scenario, the IT team manually resized the existing Azure VM, which is the literal definition of vertical scaling. Unlike horizontal scaling, no additional VM instances are created. Note that resizing a VM typically requires a restart, which may cause temporary downtime.
- ✗
Diagonal scaling
Why it's wrong here
Diagonal scaling is not a recognized scaling model in cloud computing; the official categories are vertical (up/down) and horizontal (out/in). Some may informally use diagonal scaling to describe a combination of both, but Azure and standard cloud architecture do not define it as a distinct approach. The described action—resizing a single VM—is purely a vertical change, so even a hybrid term would not best describe it. Therefore, this option is a distractor and must be marked wrong.
When this WOULD be correct
A question might ask about a scenario where an application is scaled both by adding more VMs (horizontal) and increasing the size of existing VMs (vertical) simultaneously, such as a distributed database that partitions data across multiple nodes and also upgrades each node's resources.
- ✗
Auto-scaling
Why it's wrong here
Auto-scaling is incorrect because it refers to automatically adjusting resource capacity based on predefined thresholds, such as CPU usage or request count, or on a defined schedule. The action in the scenario was a manual resize performed by the IT team, with no evidence that an Azure Autoscale rule or automation triggered it. Autoscale changes the number of running instances (scale out/in) or adjusts service capacity according to rules; it does not resize an individual VM to a larger SKU in the same way. Because the core differentiator is manual action versus automated response, this option does not fit.
When this WOULD be correct
An exam scenario where a company has a web app that experiences variable traffic and they configure Azure VM Scale Sets to automatically add or remove VM instances based on CPU usage thresholds. This would be auto-scaling (horizontal scaling).
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 scalingCorrect answer▾
Why this is correct
Vertical scaling, also known as scaling up, increases the capacity of a single resource by upgrading its specifications, such as moving a virtual machine to a larger SKU with more vCPUs and RAM. In this scenario, the IT team manually resized the existing Azure VM, which is the literal definition of vertical scaling. Unlike horizontal scaling, no additional VM instances are created. Note that resizing a VM typically requires a restart, which may cause temporary downtime.
✗Horizontal scalingWrong answer — click to see why▾
Why this is wrong here
Horizontal scaling involves adding more instances (e.g., VMs) to distribute load, but the question states the application cannot run on multiple servers simultaneously, making vertical scaling (increasing the size of the existing VM) the correct approach.
★ When this WOULD be the correct answer
This option would be correct in a scenario where an application is designed to run across multiple servers (e.g., a web app with a load balancer) and the team adds more VMs to handle increased traffic, such as adding two more VMs to a web server farm.
Why candidates choose this
Candidates often confuse scaling concepts, thinking that any increase in capacity is 'horizontal' because they associate scaling with adding resources, but they overlook the key constraint that the application cannot run on multiple servers.
✗Diagonal scalingWrong answer — click to see why▾
Why this is wrong here
Diagonal scaling is not a standard cloud scaling term; the question describes increasing the size of a single VM (more vCPUs and RAM), which is vertical scaling, not a combination of vertical and horizontal scaling.
★ When this WOULD be the correct answer
A question might ask about a scenario where an application is scaled both by adding more VMs (horizontal) and increasing the size of existing VMs (vertical) simultaneously, such as a distributed database that partitions data across multiple nodes and also upgrades each node's resources.
Why candidates choose this
Candidates may confuse 'diagonal scaling' with a real concept or think it refers to a mix of vertical and horizontal scaling, but it is not an official term in cloud computing.
✗Auto-scalingWrong answer — click to see why▾
Why this is wrong here
Auto-scaling refers to automatically adjusting resources (e.g., adding or removing VMs) based on demand, but the question describes manually increasing the VM size (vertical scaling), not automatic scaling.
★ When this WOULD be the correct answer
An exam scenario where a company has a web app that experiences variable traffic and they configure Azure VM Scale Sets to automatically add or remove VM instances based on CPU usage thresholds. This would be auto-scaling (horizontal scaling).
Why candidates choose this
Candidates may confuse 'scaling up' (vertical) with 'auto-scaling' because both involve adjusting resources to meet demand, but auto-scaling implies automation and typically horizontal scaling.
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.