MS-900 Describe cloud concepts Practice Question
A company uses a cloud service where they can rent virtual machines and storage. They have full control over the operating system and applications, while the provider manages the physical hardware. Which cloud service model is being used?
⚠ Common exam trap
Candidates often confuse IaaS with PaaS because both involve cloud-hosted resources, but the key differentiator is control over the operating system—IaaS gives OS control, PaaS does not.
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
✓
Infrastructure as a Service (IaaS)
This scenario describes Infrastructure as a Service (IaaS) because the company rents virtual machines and storage, retains full control over the operating system and applications, while the cloud provider manages the underlying physical hardware. In IaaS, the provider abstracts the physical infrastructure (servers, networking, storage) and delivers it as on-demand virtualized resources, which aligns with the customer's responsibility for OS and app configuration.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Infrastructure as a Service (IaaS)
Why this is correct
IaaS delivers virtualized computing resources, such as virtual machines, storage, and virtual networks, on demand over the internet. The consumer retains full administrative control over the guest operating system, middleware, and applications, while the cloud provider manages physical servers, storage hardware, and hypervisor virtualization. This makes it ideal for hosting legacy workloads or running custom software without maintaining physical data center infrastructure.
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Platform as a Service (PaaS)
Why it's wrong here
PaaS is a managed hosting platform where developers deploy applications using built-in tools, databases, and runtime environments, such as Azure App Service. The provider patches the underlying servers, operating systems, and middleware, so customers do not control or manage the OS-level configuration. Attempting to rent raw virtual machines and manually manage the entire stack would be below the level of abstraction PaaS provides, and lacks the user's direct server control.
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Software as a Service (SaaS)
Why it's wrong here
SaaS provides fully functional, end-user applications, such as Microsoft 365 or Salesforce, delivered through a browser or client with no user management of the underlying servers or OS. The provider manages everything from application code and data to the infrastructure, so the consumer only uses the software features. Renting virtual machines implies responsibility for the operating system and applications, which contradicts the 'no management' consumer experience of SaaS.
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On-premises deployment
Why it's wrong here
On-premises deployment involves installing and running all hardware, virtualization, and software in an organization's own data center, with the organization bearing the full cost of purchasing, patching, and managing every component. This is not a cloud service model at all, because there is no third-party cloud provider renting out resources. Renting virtual machines from a cloud provider transfers the hardware management burden to a vendor, the direct opposite of on-premises ownership.
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