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.
A company runs a virtual machine in Azure that hosts a web application. The company is responsible for configuring the operating system, installing web server software, and managing application updates. The cloud provider is responsible for the physical hardware, networking, and data center security. Which cloud service model does this represent?
Why wrong: In SaaS, the provider manages the entire application stack, and the customer only uses the software; not fitting the scenario.
B
Platform as a Service (PaaS)
Why wrong: PaaS manages the runtime environment, OS, and middleware, leaving the customer only to deploy code; here the customer manages the OS.
C
Infrastructure as a Service (IaaS)
IaaS provides virtual machines where the customer installs and configures the OS and applications, matching the described responsibilities.
D
Function as a Service (FaaS)
Why wrong: FaaS is a serverless computing model where code runs in response to events and the provider manages all infrastructure; not applicable here.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Infrastructure as a Service (IaaS)
This scenario describes Infrastructure as a Service (IaaS) because the customer manages the operating system, web server software, and application updates, while the cloud provider handles the physical hardware, networking, and data center security. In IaaS, the provider offers virtualized computing resources over the internet, and the customer retains control over the guest OS and installed software, which matches the responsibilities outlined.
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.
✗
Software as a Service (SaaS)
Why it's wrong here
In SaaS, the provider manages the entire application stack, and the customer only uses the software; not fitting the scenario.
✗
Platform as a Service (PaaS)
Why it's wrong here
PaaS manages the runtime environment, OS, and middleware, leaving the customer only to deploy code; here the customer manages the OS.
✓
Infrastructure as a Service (IaaS)
Why this is correct
IaaS provides virtual machines where the customer installs and configures the OS and applications, matching the described responsibilities.
Related concept
Read the scenario before looking for a memorised answer.
✗
Function as a Service (FaaS)
Why it's wrong here
FaaS is a serverless computing model where code runs in response to events and the provider manages all infrastructure; not applicable here.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse PaaS with IaaS because both involve deploying applications, but the key differentiator is whether the customer manages the OS and installed software—PaaS abstracts the OS, while IaaS does not.
Trap categories for this question
Scenario analysis trap
In SaaS, the provider manages the entire application stack, and the customer only uses the software; not fitting the scenario.
Detailed technical explanation
How to think about this question
In IaaS, the provider uses hypervisors (e.g., Hyper-V or KVM) to virtualize hardware, and the customer interacts with the VM via Remote Desktop Protocol (RDP) or SSH to configure the OS and install software like Apache or IIS. A real-world scenario is migrating an on-premises web server to Azure VMs, where the customer must still patch the OS and manage the web server, while Azure handles physical host failures and network redundancy. This contrasts with PaaS, where the provider automatically applies OS patches and the customer only manages application code.
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: Infrastructure as a Service (IaaS) — This scenario describes Infrastructure as a Service (IaaS) because the customer manages the operating system, web server software, and application updates, while the cloud provider handles the physical hardware, networking, and data center security. In IaaS, the provider offers virtualized computing resources over the internet, and the customer retains control over the guest OS and installed software, which matches the responsibilities outlined.
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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