This MS-900 practice question tests your understanding of describe cloud concepts. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An e-commerce company hosts its website on a public cloud IaaS platform. The site experiences varying traffic throughout the year. The cloud provider automatically adds more virtual servers during peak traffic and removes them when demand drops. The company only pays for the resources used during each period. Which two cloud characteristics are demonstrated? (Choose two.)
Correct. The automatic addition and removal of VMs based on traffic demonstrates rapid elasticity.
B
Measured service
Correct. Paying only for the resources used is a demonstration of measured service (metered billing).
C
On-demand self-service
Why wrong: Incorrect. While the company can provision resources without human interaction, the scenario emphasizes automatic scaling rather than user-initiated provisioning.
D
Resource pooling
Why wrong: Incorrect. Resource pooling refers to the provider serving multiple customers from shared infrastructure, which is not directly illustrated by the scaling scenario.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Rapid elasticity
Rapid elasticity is demonstrated because the cloud provider automatically scales virtual servers up or down in response to varying traffic, which is a key characteristic of cloud computing where resources can be provisioned and released elastically to match demand. Measured service is demonstrated because the company only pays for the resources used during each period, meaning the provider meters resource usage (e.g., CPU hours, memory, bandwidth) and bills accordingly, which is a core attribute of cloud services.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Rapid elasticity
Why this is correct
Correct. The automatic addition and removal of VMs based on traffic demonstrates rapid elasticity.
Related concept
Read the scenario before looking for a memorised answer.
✓
Measured service
Why this is correct
Correct. Paying only for the resources used is a demonstration of measured service (metered billing).
Related concept
Read the scenario before looking for a memorised answer.
✗
On-demand self-service
Why it's wrong here
Incorrect. While the company can provision resources without human interaction, the scenario emphasizes automatic scaling rather than user-initiated provisioning.
✗
Resource pooling
Why it's wrong here
Incorrect. Resource pooling refers to the provider serving multiple customers from shared infrastructure, which is not directly illustrated by the scaling scenario.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'on-demand self-service' with automatic scaling, but on-demand self-service is about manual provisioning without provider interaction, not about the system's ability to scale automatically based on load.
Trap categories for this question
Scenario analysis trap
Incorrect. While the company can provision resources without human interaction, the scenario emphasizes automatic scaling rather than user-initiated provisioning.
Detailed technical explanation
How to think about this question
Under the hood, rapid elasticity relies on orchestration tools (e.g., AWS Auto Scaling, Azure VM Scale Sets) that use metrics like CPU utilization or request count to trigger API calls to the hypervisor or cloud controller to spin up or tear down VMs, often within minutes. Measured service is implemented via metering agents that track resource consumption at a granular level (e.g., per-second billing for compute instances) and feed data into a billing system that applies a pay-as-you-go model, as defined by the NIST SP 800-145 standard. In a real-world scenario, an e-commerce site using Azure VM Scale Sets might see a 10x increase in VMs during Black Friday, with billing calculated per minute, demonstrating both elasticity and metering.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this MS-900 question in full detail.
Describe cloud concepts — This question tests Describe cloud concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Rapid elasticity — Rapid elasticity is demonstrated because the cloud provider automatically scales virtual servers up or down in response to varying traffic, which is a key characteristic of cloud computing where resources can be provisioned and released elastically to match demand. Measured service is demonstrated because the company only pays for the resources used during each period, meaning the provider meters resource usage (e.g., CPU hours, memory, bandwidth) and bills accordingly, which is a core attribute of cloud services.
What should I do if I get this MS-900 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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