AZ-900 Describe cloud concepts Practice Question
A company runs a web application that experiences sudden spikes in traffic during promotional events. They want to automatically add more virtual machines during high demand and remove them when traffic subsides, paying only for the resources used. Which cloud computing benefit does this scenario describe?
⚠ Common exam trap
Many candidates confuse elasticity with scalability, but the key differentiator is that elasticity implies automatic, dynamic scaling in response to real-time demand and pay-per-use billing, whereas scalability can be a manual or planned capacity change without the automatic or cost-efficiency aspects.
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
This scenario describes elasticity, which is the ability of a cloud system to automatically provision and de-provision resources (such as virtual machines) in response to real-time demand changes. The key phrase 'automatically add more virtual machines during high demand and remove them when traffic subsides, paying only for the resources used' directly matches the cloud computing benefit of elasticity, where scaling is dynamic and resource usage is metered, ensuring cost efficiency.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Elasticity
Why this is correct
Elasticity automatically provisions and releases cloud resources in real time to match fluctuating workloads, like sudden spikes, without manual intervention. This means the application scales out during demand surges and scales in when traffic drops, and you are billed only for the resources actually consumed at each point in time.
- ✗
Scalability
Why it's wrong here
Scalability is the capability to handle increased workload by adding resources, either by increasing the size of existing resources or adding more instances, and it is essential for growth. However, scaling can be manual or require advance planning, and it typically does not release unused resources when demand falls; elasticity is the specific form of scalability that automatically scales both up and down in response to real-time demand.
When this WOULD be correct
A company expects steady growth in user traffic over the next year and wants to ensure their application can handle the increased load by adding more virtual machines permanently. Which cloud computing benefit does this describe?
- ✗
High availability
Why it's wrong here
High availability keeps an application accessible by using redundant infrastructure across multiple availability zones or regions, with failover and load balancing that mask component failures. It is designed to minimize downtime and meet uptime SLAs, but it does not automatically adjust capacity in response to demand spikes, so resources remain static regardless of sudden traffic increases.
When this WOULD be correct
A question describing a system designed to remain operational with minimal downtime during a regional outage, using multiple availability zones or redundant components, would make high availability the correct answer.
- ✗
Fault tolerance
Why it's wrong here
Fault tolerance is the ability of an application to continue operating correctly and without interruption even when one or more components, such as a server or network device, fail. It achieves this through redundant components and automatic failover that detect and replace failures, but it does not scale resources up or down based on load, so it cannot help with sudden spikes.
When this WOULD be correct
A question asks: 'A company wants its application to remain operational even if a single server fails. Which benefit ensures the system continues functioning without downtime?' In that case, fault tolerance would be correct as it maintains operations despite 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 automatically provisions and releases cloud resources in real time to match fluctuating workloads, like sudden spikes, without manual intervention. This means the application scales out during demand surges and scales in when traffic drops, and you are billed only for the resources actually consumed at each point in time.
✗ScalabilityWrong answer — click to see why▾
Why this is wrong here
Scalability refers to the ability to handle increased load by adding resources, but it does not inherently include automatic removal of resources when demand decreases, nor does it emphasize paying only for what is used. The scenario specifically describes automatic scaling up and down based on demand, which is elasticity.
★ When this WOULD be the correct answer
A company expects steady growth in user traffic over the next year and wants to ensure their application can handle the increased load by adding more virtual machines permanently. Which cloud computing benefit does this describe?
Why candidates choose this
Candidates often confuse scalability with elasticity because both involve adding resources to meet demand, but they overlook that elasticity includes automatic scaling in both directions and pay-per-use, which is the key differentiator in this scenario.
✗High availabilityWrong answer — click to see why▾
Why this is wrong here
High availability focuses on ensuring the application remains accessible despite failures (e.g., via redundancy across zones), not on automatically adjusting capacity in response to traffic spikes.
★ When this WOULD be the correct answer
A question describing a system designed to remain operational with minimal downtime during a regional outage, using multiple availability zones or redundant components, would make high availability the correct answer.
Why candidates choose this
Candidates may confuse the ability to handle increased load (elasticity) with the concept of keeping the system always up (high availability), especially when the scenario involves traffic spikes that could cause downtime if not managed.
✗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 automatically adjusting resources based on demand. The scenario describes adding/removing VMs to match traffic spikes, which is elasticity, not fault tolerance.
★ When this WOULD be the correct answer
A question asks: 'A company wants its application to remain operational even if a single server fails. Which benefit ensures the system continues functioning without downtime?' In that case, fault tolerance would be correct as it maintains operations despite failures.
Why candidates choose this
Candidates may confuse fault tolerance with elasticity because both involve handling disruptions (traffic spikes vs. failures), leading them to select a term that sounds like it deals with unexpected events.
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.
About these practice questions
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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.