MS-900 Describe cloud concepts Practice Question
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?
⚠ Common exam trap
Many exam-takers confuse 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.
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 and PaaS
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.
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 automatically adjusts computing capacity in real time to match fluctuating demand, while PaaS offloads management of the underlying OS, runtime, and middleware to the provider. This combination fits the scenario because the customer can scale the application on demand without handling infrastructure patching, while the provider maintains the platform. Unlike IaaS, the OS is not the customer's responsibility; unlike SaaS, the application itself remains under customer control.
- ✗
Scalability and IaaS
Why it's wrong here
Scalability alone is too general: it can describe planned vertical or horizontal expansion that does not necessarily happen automatically or rapidly. More critically, IaaS delivers raw virtual machines, storage, and networking, leaving the customer responsible for configuring, securing, and patching the guest operating system. Because the scenario specifies the provider managing the OS, IaaS contradicts that stated responsibility, so pairing scalability with IaaS cannot be correct.
- ✗
Rapid elasticity and SaaS
Why it's wrong here
Rapid elasticity is indeed a core cloud characteristic, but in SaaS the service provider owns the entire application stack and weaves scaling into the multitenant platform, which tenants cannot directly control or invoke. The operating system is completely abstracted and managed by the vendor, so there is no OS for the customer to manage or patch, unlike the division of labor implied in the question. Thus, while the wording partially describes cloud behavior, it mismatches the responsibilities described for an application-level service.
- ✗
Measured service and PaaS
Why it's wrong here
Measured service is about usage metering and pay-per-use billing, such as monitoring VM hours or storage consumption; it does nothing to automatically scale resources or transfer OS and platform maintenance to the provider. Although PaaS does provide OS and platform management, combining it with measured service fails to explain the rapid, demand-driven scaling capability mentioned in the scenario. Elasticity is the missing characteristic, making this pairing incorrect despite PaaS's correct service model.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This MS-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 MS-900 exam.