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.
A company is deploying a cloud solution where they have the ability to quickly scale up resources during peak demand and scale down during off-peak hours, paying only for what they use. They also need the provider to automatically manage the underlying platform, including patching the operating system. Which combination of cloud characteristics and service model best describes this scenario?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Elasticity allows rapid scaling based on demand; PaaS manages the OS and platform, matching the provider responsibilities described.
B
Scalability and IaaS
Why wrong: Scalability is a broader term; IaaS requires the customer to manage the OS, not the provider.
C
Rapid elasticity and SaaS
Why wrong: SaaS provides fully managed applications, but the customer typically does not control scaling; also SaaS does not expose OS patching to the customer.
D
Measured service and PaaS
Why wrong: Measured service refers to metering and billing for usage, not automatically scaling resources or managing the OS.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Elasticity and PaaS
Option A is correct because the scenario describes elasticity (the ability to scale resources up and down automatically based on demand) and Platform as a Service (PaaS), where the provider manages the underlying platform, including OS patching. Elasticity is a key cloud characteristic that enables dynamic scaling, and PaaS abstracts infrastructure management, aligning perfectly with the requirement for automatic platform maintenance.
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.
✓
Elasticity and PaaS
Why this is correct
Elasticity allows rapid scaling based on demand; PaaS manages the OS and platform, matching the provider responsibilities described.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Scalability and IaaS
Why it's wrong here
Scalability is a broader term; IaaS requires the customer to manage the OS, not the provider.
✗
Rapid elasticity and SaaS
Why it's wrong here
SaaS provides fully managed applications, but the customer typically does not control scaling; also SaaS does not expose OS patching to the customer.
✗
Measured service and PaaS
Why it's wrong here
Measured service refers to metering and billing for usage, not automatically scaling resources or managing the OS.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing scalability (a general capability) with elasticity (dynamic, automated scaling), and assuming IaaS includes platform management like patching, which it does not—IaaS only provides virtual machines where the customer handles the OS.
Detailed technical explanation
How to think about this question
Elasticity in cloud computing is often implemented via auto-scaling groups that use metrics like CPU utilization or request count to trigger scale-out/in actions, with a cooldown period to avoid thrashing. In PaaS, the provider handles OS patching through automated update mechanisms (e.g., Azure App Service applies OS patches during maintenance windows), while the customer only manages application code and configuration. A real-world example is an e-commerce site on Azure App Service that scales out during Black Friday and scales down afterward, with no customer involvement in patching the underlying Windows or Linux VMs.
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: Elasticity and PaaS — Option A is correct because the scenario describes elasticity (the ability to scale resources up and down automatically based on demand) and Platform as a Service (PaaS), where the provider manages the underlying platform, including OS patching. Elasticity is a key cloud characteristic that enables dynamic scaling, and PaaS abstracts infrastructure management, aligning perfectly with the requirement for automatic platform maintenance.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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