This MS-900 practice question tests your understanding of describe cloud concepts. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 website hosted on a cloud provider automatically adds more virtual machines to handle increased traffic during Black Friday and removes them after the event. Which cloud characteristic does this illustrate?
Correct. The automatic scaling of VMs up and down in response to traffic spikes demonstrates rapid elasticity.
B
On-demand self-service
Why wrong: Incorrect. On-demand self-service refers to a user's ability to provision resources without human interaction, not the automatic scaling behavior.
C
Resource pooling
Why wrong: Incorrect. Resource pooling is about sharing infrastructure among multiple customers, not dynamic scaling.
D
Measured service
Why wrong: Incorrect. Measured service involves tracking usage for billing, not the ability to scale resources.
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 the cloud characteristic that enables resources to scale out (add VMs) automatically in response to demand spikes like Black Friday traffic, and scale in (remove VMs) when demand subsides. This is distinct from manual scaling because it happens automatically and dynamically, often using autoscaling policies tied to metrics such as CPU utilization or request count.
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 scaling of VMs up and down in response to traffic spikes demonstrates rapid elasticity.
Related concept
Read the scenario before looking for a memorised answer.
✗
On-demand self-service
Why it's wrong here
Incorrect. On-demand self-service refers to a user's ability to provision resources without human interaction, not the automatic scaling behavior.
✗
Resource pooling
Why it's wrong here
Incorrect. Resource pooling is about sharing infrastructure among multiple customers, not dynamic scaling.
✗
Measured service
Why it's wrong here
Incorrect. Measured service involves tracking usage for billing, not the ability to scale resources.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse 'rapid elasticity' with 'on-demand self-service' because both involve automation, but elasticity specifically refers to automatic scaling in response to load, not just the ability to provision resources on demand.
Detailed technical explanation
How to think about this question
Under the hood, rapid elasticity is implemented via orchestration tools (e.g., AWS Auto Scaling, Azure VM Scale Sets) that use health probes and scaling rules (e.g., add 2 VMs when average CPU > 70% for 5 minutes) to adjust capacity. A subtle behavior is that elasticity can be horizontal (adding/removing instances) or vertical (resizing existing instances), but horizontal is more common for stateless web tiers. In real-world scenarios, improperly configured cooldown periods can cause thrashing, where VMs are added and removed too quickly, leading to cost spikes or instability.
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 the cloud characteristic that enables resources to scale out (add VMs) automatically in response to demand spikes like Black Friday traffic, and scale in (remove VMs) when demand subsides. This is distinct from manual scaling because it happens automatically and dynamically, often using autoscaling policies tied to metrics such as CPU utilization or request count.
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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Question Discussion
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