What is SaaS in Cloud Computing for Microsoft 365?
An organization uses Microsoft 365 E5 licenses. Users report that Microsoft 365 Apps for enterprise (e.g., Word, Excel) are slow to open. The IT team considers deploying a cloud-based solution to improve performance. Which cloud service model should they use?
Quick Answer
Software as a Service is the right classification here because Microsoft 365 Apps for enterprise is already delivered that way — Microsoft hosts, patches, and updates the applications, and the organization only manages user access and data. The scenario is really testing whether you recognise that switching to a cloud-based solution to fix slow-opening desktop apps means leaning further into the SaaS delivery model already in place, such as favouring the web-based Office apps over locally cached installs, rather than pointing at IaaS or PaaS, which would require the company to manage infrastructure or a runtime it has no reason to take on. The distinction worth keeping straight for the exam: SaaS is complete software delivered over the internet with nothing for the customer to install or maintain beyond the client, which is exactly what Word, Excel, and the rest of the Microsoft 365 Apps suite already are.
⚠ Common exam trap
Many candidates confuse the need for a cloud-based solution with IaaS or PaaS, thinking they need to build or host the applications themselves, when the organization already has the SaaS solution (Microsoft 365) and just needs to optimize its delivery or use the web-based SaaS versions.
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)
The organization is already using Microsoft 365 Apps for enterprise, which are delivered as a SaaS offering. To improve performance for slow-opening desktop apps, deploying a cloud-based solution means leveraging the same SaaS model—Microsoft 365 Apps are already SaaS. The issue is likely related to local installation or network latency, and using the web-based versions (also SaaS) or optimizing the existing SaaS delivery can help. Option B is correct because SaaS provides ready-to-use applications like Word and Excel via the cloud, eliminating local installation overhead.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Platform as a Service (PaaS)
Why it's wrong here
PaaS is for developing and deploying custom applications, not for standard Office apps.
- ✓
Software as a Service (SaaS)
Why this is correct
SaaS delivers Microsoft 365 Apps via the cloud, optimized for performance and reduced local load.
- ✗
Infrastructure as a Service (IaaS)
Why it's wrong here
IaaS would require virtual machines and manual installation of Office, not improving performance directly.
- ✗
Function as a Service (FaaS)
Why it's wrong here
FaaS runs code in response to events, not relevant to Office performance.
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Same concept, more angles
1 more way this is tested on MS-900
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Your organization uses Microsoft 365 and wants to provide employees with access to corporate resources from their personal devices without managing the entire device. Which cloud service model is being used?
easy- A.Infrastructure as a Service (IaaS)
- B.Platform as a Service (PaaS)
- C.Desktop as a Service (DaaS)
- ✓ D.Software as a Service (SaaS)
Why D: Software as a Service (SaaS) is the correct cloud service model because Microsoft 365 is a SaaS offering. Users access applications like Exchange Online, SharePoint, and Teams over the internet without managing the underlying infrastructure or the devices. IaaS provides virtual machines and storage, PaaS provides a platform for custom applications, and DaaS delivers virtual desktops, but none match the scenario of using corporate SaaS apps from personal devices without device management.
JA
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.