AZ-900 Describe cloud concepts Practice Question
A company runs an e-commerce website on a set of on-premises servers that are fully owned and depreciated. The website experiences predictable traffic surges during seasonal sales. The company plans to migrate to Azure and wants to pay only for the compute and storage resources consumed, with the ability to automatically add virtual machines during sales and remove them afterward. Which characteristic of cloud computing does this scenario best illustrate?
⚠ Common exam trap
Candidates often confuse elasticity with high availability or fault tolerance, mistakenly thinking that automatically adding VMs during traffic surges is about keeping the system available or resilient to failures, rather than about dynamic scaling to match demand.
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 cloud computing characteristic that allows resources to automatically scale out (add virtual machines) during demand spikes like seasonal sales and scale in (remove VMs) when demand drops, aligning with the pay-per-use model. This scenario directly matches elasticity because the company wants to dynamically adjust compute and storage resources in response to predictable traffic surges, paying only for what is consumed.
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 designing systems to remain operational with minimal downtime, often through redundancy (e.g., multiple servers, availability zones). While important, it does not directly address the automatic scaling of resources based on demand or the pay-per-use billing model.
When this WOULD be correct
An exam question describing a company that needs its e-commerce website to remain operational with minimal downtime during a regional Azure outage, achieved by deploying VMs across multiple availability zones, would make high availability the correct answer.
- ✓
Elasticity
Why this is correct
Elasticity is the ability to dynamically allocate and deallocate cloud resources in response to changing workload demands. The company wants to automatically add VMs during sales traffic spikes and remove them afterward, paying only for what is used. This is a classic example of elasticity.
- ✗
Fault tolerance
Why it's wrong here
Fault tolerance is the ability of a system to continue operating correctly, without interruption, when one or more of its components fail (e.g., a server, network link, or power supply). In an on-premises e-commerce scenario, you might achieve this through redundant hardware or clustering, but the stated business need is to automatically adjust VM capacity in response to sales traffic spikes. Fault tolerance addresses resilience to failures, not dynamic scaling to meet fluctuating demand, and it does not inherently align with the pay-per-use model described in the scenario.
When this WOULD be correct
An exam question describing a system that must remain operational without interruption even if a server fails, such as a critical financial trading platform that requires zero downtime during hardware failures, would make fault tolerance the correct answer.
- ✗
Disaster recovery
Why it's wrong here
Disaster recovery (DR) encompasses the policies, tools, and procedures for restoring IT infrastructure and data after a major disruptive event, such as a natural disaster, large-scale cyberattack, or regional outage. The company's requirement is to handle predictable, short-term increases in demand during sales events by adding and removing VMs automatically, which is a scaling concern rather than a recovery concern. DR typically involves recovery time objectives (RTO) and recovery point objectives (RPO), and it does not address the continuous, automatic provisioning and deprovisioning of compute resources based on real-time workload.
When this WOULD be correct
A company experiences a major outage due to a natural disaster and needs to restore its e-commerce platform from backups in a secondary Azure region. The question asks which cloud characteristic enables business continuity after such an event.
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 ability to dynamically allocate and deallocate cloud resources in response to changing workload demands. The company wants to automatically add VMs during sales traffic spikes and remove them afterward, paying only for what is used. This is a classic example of elasticity.
✗High availabilityWrong answer — click to see why▾
Why this is wrong here
High availability focuses on minimizing downtime and ensuring service continuity, not on dynamically scaling resources up and down based on demand. The scenario describes automatic addition and removal of VMs to match traffic surges, which is elasticity.
★ When this WOULD be the correct answer
An exam question describing a company that needs its e-commerce website to remain operational with minimal downtime during a regional Azure outage, achieved by deploying VMs across multiple availability zones, would make high availability the correct answer.
Why candidates choose this
Candidates may confuse high availability with the ability to handle increased load, but high availability is about redundancy and uptime, not dynamic scaling of resources.
✗Fault toleranceWrong answer — click to see why▾
Why this is wrong here
Fault tolerance refers to a system's ability to continue operating despite component failures, not to automatically scaling resources up and down based on demand. The scenario describes scaling compute resources to handle traffic surges, which is elasticity.
★ When this WOULD be the correct answer
An exam question describing a system that must remain operational without interruption even if a server fails, such as a critical financial trading platform that requires zero downtime during hardware failures, would make fault tolerance the correct answer.
Why candidates choose this
Candidates may confuse fault tolerance with the ability to handle increased load, or they may think that automatically adding VMs during sales is a form of tolerating the 'fault' of high traffic.
✗Disaster recoveryWrong answer — click to see why▾
Why this is wrong here
Disaster recovery focuses on restoring systems and data after a catastrophic failure, not on dynamically scaling resources up and down based on demand. The scenario describes automatic scaling to handle traffic surges, which is elasticity.
★ When this WOULD be the correct answer
A company experiences a major outage due to a natural disaster and needs to restore its e-commerce platform from backups in a secondary Azure region. The question asks which cloud characteristic enables business continuity after such an event.
Why candidates choose this
Candidates may confuse disaster recovery with the ability to handle increased load, or they might think that automatically adding VMs during sales is a form of recovery from a 'disaster' of high traffic.
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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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.