MS-900 Describe cloud concepts Practice Question
A company wants to use a cloud service that provides ready-to-use business applications such as email, collaboration, and customer relationship management without managing the underlying infrastructure. Which cloud service model is this?
⚠ Common exam trap
Candidates often confuse PaaS with SaaS because both abstract infrastructure, but PaaS requires the customer to develop and manage the application code, whereas SaaS provides fully functional, ready-to-use applications—a distinction Microsoft emphasizes in the MS-900 by focusing on the 'what you manage' vs. 'what the provider manages' model.
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
✓
Software as a Service (SaaS)
(SaaS) is correct because Software as a Service delivers ready-to-use business applications like Microsoft 365 (Exchange Online for email, Teams for collaboration, Dynamics 365 for CRM) over the internet, with the provider managing all underlying infrastructure, including servers, storage, and networking. The customer simply accesses the software via a web browser or client app without any responsibility for patching, scaling, or hardware 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.
- ✗
Infrastructure as a Service (IaaS)
Why it's wrong here
IaaS provides virtualized computing resources such as VMs, storage, and networking, but leaves the operating system, runtime, and application stack to the customer. This means users must build, deploy, and manage their own business applications on top, rather than receiving ready-to-use business software. The provider only manages the underlying physical infrastructure.
- ✗
Platform as a Service (PaaS)
Why it's wrong here
PaaS offers a managed hosting and development environment, including application runtimes, databases, and middleware, yet it still requires code to be written or customized before a business application exists. It targets developers who need to deploy and scale custom apps, not business users looking for immediately usable tools like email or CRM. Without development effort, no ready-made business functionality is delivered.
- ✓
Software as a Service (SaaS)
Why this is correct
SaaS is a complete, cloud-hosted application delivered over the internet, where the provider manages the entire stack—from infrastructure and middleware to security patches and version updates. Subscribers access the ready-to-use business functionality via a browser or mobile app, needing no installation or development, as exemplified by Exchange Online and Dynamics 365. This model aligns directly with the requirement of using a cloud service that provides ready-to-use business applications.
- ✗
Private cloud
Why it's wrong here
Private cloud is a deployment architecture in which cloud infrastructure is provisioned for exclusive use by a single organization, either on-premises or hosted, rather than a classification of what capability the cloud delivers. It does not, by itself, supply ready-made business applications; an organization could run IaaS, PaaS, or SaaS on it, but the service model must still be chosen. Therefore, it cannot be the correct answer to a question asking for a service model offering ready-to-use business software.
Go deeper
Related to this question
Learn chapter
Hybrid Exchange and Mail Migration
Key term
Collaboration
Collaboration in Microsoft 365 refers to the integrated tools and services that enable people to work together in real time, share information, and coordinate tasks from anywhere.
Key term
Exchange Online
Exchange Online is Microsoft's cloud-based email, calendar, and contact hosting service that is part of the Microsoft 365 suite, allowing organizations to manage corporate messaging without maintaining their own mail servers.
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