AZ-900 Describe cloud concepts Practice Question
A company runs a web application in Azure that experiences variable traffic throughout the day. During peak hours, the application becomes slow because the existing virtual machine (VM) cannot handle the increased load. The solution architect proposes adding more VMs of the same size and distributing incoming requests across all of them to balance the load. Which scaling concept does this approach represent?
⚠ Common exam trap
Many exam-takers confuse 'horizontal scaling' with 'elastic scaling' because both involve adding resources, but elastic scaling is an automated behavior (autoscaling) that can implement either horizontal or vertical scaling, not a distinct scaling concept itself.
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
✓
Horizontal scaling
Horizontal scaling (also known as scaling out) involves adding more virtual machines of the same size to distribute incoming traffic across them. In this scenario, adding more VMs of the same size and using a load balancer to distribute requests directly matches the definition of horizontal scaling, which increases system capacity by adding more instances rather than increasing the power of a single instance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Vertical scaling
Why it's wrong here
Vertical scaling (scaling up) means increasing the capacity of a single resource, such as upgrading the existing VM to a larger SKU with more CPU cores or memory. The scenario describes adding more VMs, not enhancing the existing one.
When this WOULD be correct
Vertical scaling would be correct if the question described upgrading the existing VM to a larger size (e.g., from Standard_D2s_v3 to Standard_D4s_v3) to handle increased load, without adding additional VMs.
- ✓
Horizontal scaling
Why this is correct
Horizontal scaling (scaling out) involves adding more instances of the same resource type and distributing the workload among them. This is exactly what is described: adding more VMs of the same size and using load balancing to distribute traffic.
- ✗
Elastic scaling
Why it's wrong here
Elastic scaling is the ability of a system to automatically scale resources up or down based on real-time demand. While the scenario involves scaling to meet increased load, it is a manual, planned addition of VMs rather than an automatic adjustment.
When this WOULD be correct
A question that asks: 'A company wants to automatically add VMs during peak hours and remove them during low traffic to optimize cost and performance. Which concept does this describe?'
- ✗
Disaster recovery
Why it's wrong here
Disaster recovery (DR) is a set of processes and policies for restoring IT infrastructure and data after a catastrophic event—such as an Azure region outage, cyberattack, or hardware failure—typically using tools like Azure Site Recovery or geo-redundant storage. The scenario describes a deliberate, proactive capacity expansion to absorb increased traffic, not a reactive recovery from an unexpected failure. Adding VMs with a load balancer is a scaling operation, whereas DR focuses on continuity of service after a disaster, often involving failover to a secondary region, not simply increasing compute instances.
When this WOULD be correct
A question asks: 'A company wants to ensure its application can fail over to a secondary Azure region if the primary region goes down. Which concept does this represent?'
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.
✓Horizontal scalingCorrect answer▾
Why this is correct
Horizontal scaling (scaling out) involves adding more instances of the same resource type and distributing the workload among them. This is exactly what is described: adding more VMs of the same size and using load balancing to distribute traffic.
✗Vertical scalingWrong answer — click to see why▾
Why this is wrong here
Vertical scaling involves increasing the capacity of a single VM (e.g., adding more CPU/RAM), not adding more VMs of the same size. The question describes adding additional VMs and distributing load, which is horizontal scaling.
★ When this WOULD be the correct answer
Vertical scaling would be correct if the question described upgrading the existing VM to a larger size (e.g., from Standard_D2s_v3 to Standard_D4s_v3) to handle increased load, without adding additional VMs.
Why candidates choose this
Candidates may confuse 'scaling up' (vertical) with 'scaling out' (horizontal) because both address performance issues, and the term 'scaling' is often used loosely without specifying direction.
✗Elastic scalingWrong answer — click to see why▾
Why this is wrong here
Elastic scaling refers to the ability to automatically add or remove resources based on demand, but the question describes a manual proposal to add more VMs, not an automated adjustment.
★ When this WOULD be the correct answer
A question that asks: 'A company wants to automatically add VMs during peak hours and remove them during low traffic to optimize cost and performance. Which concept does this describe?'
Why candidates choose this
Candidates confuse horizontal scaling (adding more VMs) with elastic scaling because both involve adjusting capacity, but elastic scaling emphasizes automation, not just the scaling direction.
✗Disaster recoveryWrong answer — click to see why▾
Why this is wrong here
Disaster recovery focuses on restoring IT systems and data after a disruptive event, not on handling variable traffic by adding VMs and distributing load.
★ When this WOULD be the correct answer
A question asks: 'A company wants to ensure its application can fail over to a secondary Azure region if the primary region goes down. Which concept does this represent?'
Why candidates choose this
Candidates may confuse disaster recovery with high availability or scaling, thinking it includes adding resources to handle increased load during failures.
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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JA
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.