AZ-900 Describe cloud concepts Practice Question
A startup runs a web application on Azure virtual machines. The application experiences sudden, short-lived spikes in traffic multiple times a day. The startup configures an autoscale rule that adds two additional VM instances when CPU usage exceeds 75% and removes them when CPU drops below 30%. This approach is designed to match resource consumption closely to demand. Which cloud computing characteristic does this scenario primarily demonstrate?
⚠ Common exam trap
Many exam-takers confuse elasticity with high availability, because both involve multiple instances, but elasticity is about scaling to meet demand while high availability is about maintaining uptime through redundancy.
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
✓
Elasticity
Elasticity is the ability of a cloud system to automatically scale resources up or down based on real-time demand. In this scenario, the autoscale rule dynamically adds two VM instances when CPU exceeds 75% and removes them when CPU drops below 30%, closely matching resource consumption to traffic spikes. This on-demand provisioning and de-provisioning of compute capacity is the defining characteristic of elasticity.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
High Availability
Why it's wrong here
High availability refers to ensuring an application or service remains operational with minimal downtime, often through redundancy and failover. While autoscaling can contribute to availability, the core purpose described here is adjusting capacity to match demand, not maintaining uptime.
When this WOULD be correct
A question that asks: 'An application is deployed across multiple Azure availability zones to ensure it remains accessible during a regional outage. Which cloud characteristic does this demonstrate?' Here, High Availability would be correct because the setup ensures continuous operation despite failures.
- ✓
Elasticity
Why this is correct
Elasticity is the cloud characteristic that enables resources to be automatically provisioned and de-provisioned in response to real-time workload changes. The autoscale rule that adds or removes VMs based on CPU usage directly embodies elasticity by ensuring resource consumption closely follows demand.
- ✗
Fault Tolerance
Why it's wrong here
Fault tolerance allows a system to continue operating without interruption when one or more components fail. Autoscaling does not inherently handle component failures; it addresses capacity changes. Fault tolerance is achieved through redundant deployments across availability zones or regions, not through scaling rules.
When this WOULD be correct
A question that asks: 'An application runs on multiple Azure VMs across two availability zones. If one zone fails, the application continues to run without downtime. Which cloud characteristic does this demonstrate?' In that case, fault tolerance would be correct because the system is designed to withstand component failures.
- ✗
Durability
Why it's wrong here
Durability refers to the ability of a system to preserve data integrity and availability against failures such as crashes, power outages, or hardware degradation through redundant storage, backups, and replication mechanisms. In this scenario, autoscaling virtual machines based on CPU utilization does not involve any data persistence or recovery processes; it only adjusts compute capacity to match demand. Even if the VMs are scaled up or down, the underlying data remains on managed disks or storage accounts with their own independent durability guarantees. Therefore, durability is not the cloud characteristic being demonstrated by this autoscaling configuration.
When this WOULD be correct
A question asking: 'A company stores critical financial records in Azure Blob Storage and requires that data remains intact even if a data center fails. Which cloud characteristic is demonstrated?' would make Durability correct, as it ensures data survives failures.
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.
✓ElasticityCorrect answer▾
Why this is correct
Elasticity is the cloud characteristic that enables resources to be automatically provisioned and de-provisioned in response to real-time workload changes. The autoscale rule that adds or removes VMs based on CPU usage directly embodies elasticity by ensuring resource consumption closely follows demand.
✗High AvailabilityWrong answer — click to see why▾
Why this is wrong here
High Availability focuses on minimizing downtime through redundancy, not on dynamically adjusting resources to match fluctuating demand. The scenario describes scaling resources up and down based on load, which is elasticity, not high availability.
★ When this WOULD be the correct answer
A question that asks: 'An application is deployed across multiple Azure availability zones to ensure it remains accessible during a regional outage. Which cloud characteristic does this demonstrate?' Here, High Availability would be correct because the setup ensures continuous operation despite failures.
Why candidates choose this
Candidates may confuse autoscaling with high availability because both involve multiple VMs, but high availability is about uptime and redundancy, not dynamic scaling to meet demand changes.
✗Fault ToleranceWrong answer — click to see why▾
Why this is wrong here
Fault tolerance refers to a system's ability to continue operating without interruption in the event of component failures, not to dynamically adjusting resources based on demand. The scenario describes scaling resources up and down to match traffic spikes, which is elasticity, not fault tolerance.
★ When this WOULD be the correct answer
A question that asks: 'An application runs on multiple Azure VMs across two availability zones. If one zone fails, the application continues to run without downtime. Which cloud characteristic does this demonstrate?' In that case, fault tolerance would be correct because the system is designed to withstand component failures.
Why candidates choose this
Candidates may confuse fault tolerance with elasticity because both involve handling changes in load or failures, but fault tolerance is about maintaining operation during failures, not scaling to meet demand.
✗DurabilityWrong answer — click to see why▾
Why this is wrong here
Durability refers to the ability to retain data without loss over time, typically through replication or backup. The scenario describes scaling resources to match demand, not data persistence.
★ When this WOULD be the correct answer
A question asking: 'A company stores critical financial records in Azure Blob Storage and requires that data remains intact even if a data center fails. Which cloud characteristic is demonstrated?' would make Durability correct, as it ensures data survives failures.
Why candidates choose this
Candidates may confuse durability with availability or resilience, thinking that maintaining performance during spikes implies data durability, but durability is about data preservation, not resource 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?”
Go deeper
Related to this question
Learn chapter
What is Cloud Computing?
Key term
Cloud computing
Cloud computing is the on-demand delivery of IT resources over the internet, allowing users to access computing power, storage, and applications without owning physical hardware.
Key term
Elasticity
Elasticity is the ability of a cloud system to automatically add or remove computing resources (like servers, storage, or bandwidth) in response to real-time changes in demand.
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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.