Choosing the Right Cloud Service
IaaS, PaaS, or SaaS? The exam will give you scenarios and expect you to pick the right service type. Let's practise with real-world decision-making.
How do you pick the right service type?
Think of it as a decision based on one question: how much do you want to manage?
Need full control over the OS and software? → IaaS (you rent the kitchen)
Just want to deploy your code without worrying about servers? → PaaS (meal kit)
Don’t want to build anything — just use a working application? → SaaS (takeaway)
The exam gives you scenarios and expects you to pick the right one. The clue is always in how much control or customisation the scenario requires.
The decision framework
| Scenario Clue | Service Type | Why |
|---|---|---|
| ”Legacy application,” “lift-and-shift,” “same OS” | IaaS | Legacy apps need specific OS configurations |
| ”Full control over the operating system” | IaaS | Only IaaS gives you OS access |
| ”Custom network configuration” | IaaS | Fine-grained networking requires IaaS |
| ”Deploy code,” “focus on development” | PaaS | PaaS handles infrastructure so you focus on code |
| ”Without managing servers” | PaaS | PaaS abstracts server management |
| ”Managed database” | PaaS | Azure SQL Database, Cosmos DB = PaaS |
| ”Ready-to-use application” | SaaS | SaaS = fully built software you subscribe to |
| ”Email, collaboration, CRM” | SaaS | Microsoft 365, Dynamics 365, Salesforce |
| ”No development needed” | SaaS | If they’re not building anything, it’s SaaS |
Scenario practice — all four characters
Scenario 1: Peak Roasters needs email
Peak Roasters’ 15 staff need professional email, calendars, and document sharing. They have no developers.
Answer: SaaS (Microsoft 365)
Why not IaaS? Running your own email server is expensive, complex, and requires 24/7 maintenance — impractical for a small team.
Why not PaaS? Email isn’t something you “develop.” You need a ready-made service.
Scenario 2: Kai builds a web API
Kai is building a REST API for their university project. They want to write Python code and have it running online without configuring servers.
Answer: PaaS (Azure App Service or Azure Functions)
Why not IaaS? Kai doesn’t want to manage VMs, install web servers, or patch operating systems.
Why not SaaS? Kai is building custom software, not using a pre-built app.
Scenario 3: Summit Construction migrates legacy software
Summit’s project management software runs on Windows Server 2019 with custom registry settings and third-party drivers. It cannot be rewritten.
Answer: IaaS (Azure Virtual Machines)
Why not PaaS? The app requires specific OS configurations that PaaS doesn’t support.
Why not SaaS? The app is custom-built, not a commercially available product.
Scenario 4: Harbour Health needs a managed database
Harbour Health’s new app needs a SQL database. They don’t want to manage patches, backups, or high availability — they want the database “just to work.”
Answer: PaaS (Azure SQL Database)
Why not IaaS? Running SQL Server on a VM means they’d manage the OS, patches, backups, and HA themselves.
Why not SaaS? A database service isn’t a complete application — it’s a platform component.
The IaaS-to-PaaS journey
Many organisations start with IaaS (lift-and-shift) to get off on-premises quickly, then gradually modernise to PaaS for reduced management overhead.
Summit Construction’s plan:
- Year 1: Lift-and-shift legacy app to Azure VMs (IaaS)
- Year 2: Rebuild the app as a modern web app on Azure App Service (PaaS)
- Ongoing: Use Microsoft 365 for email and collaboration (SaaS)
This “crawl, walk, run” approach is a common exam scenario: identifying where an organisation is in their cloud journey and what they should do next.
Common exam traps
Exam traps to watch for
Trap 1: “Azure SQL Database is IaaS because databases run on servers” ❌ Wrong. Azure SQL Database is PaaS. Microsoft manages the server, OS, and database engine. If you want IaaS for SQL, you’d install SQL Server on a VM yourself.
Trap 2: “Serverless means no servers” ❌ Wrong. Servers exist — you just don’t manage them. Serverless is a form of PaaS with consumption-based billing.
Trap 3: “SaaS means you have no responsibility” ❌ Wrong. You’re still responsible for your data, identity, and access. If you share a sensitive document in Microsoft 365, that’s your responsibility, not Microsoft’s.
Trap 4: “You should always use PaaS because it’s cheaper” ❌ Wrong. PaaS is cheaper to operate but sometimes you NEED IaaS — for legacy apps, custom OS, or specific compliance requirements.
Quick reference: Azure services by type
| IaaS | PaaS | SaaS |
|---|---|---|
| Azure Virtual Machines | Azure App Service | Microsoft 365 |
| Azure Virtual Network | Azure SQL Database | Dynamics 365 |
| Azure Disk Storage | Azure Functions | Power BI (cloud) |
| Azure Load Balancer | Azure Cosmos DB | Microsoft Intune |
| Network Security Groups | Azure Kubernetes Service | OneDrive |
Note: Some services blur the lines. Azure Kubernetes Service (AKS) is PaaS at the cluster level but gives you IaaS-like control over containers. The exam keeps it straightforward at the fundamentals level.
🎬 Video walkthrough
Flashcards
Knowledge Check
A company has a 10-year-old application that requires Windows Server 2016 with specific registry settings and custom drivers. They want to move it to Azure. Which approach should they use?
A startup wants to build and deploy a new web application. They want to focus on writing code without managing operating systems or web servers. Which service model is BEST suited?
Which of the following Azure services is an example of PaaS? (Select TWO)
🎉 You’ve completed Domain 1: Cloud Concepts! You now understand cloud computing, deployment models, pricing, benefits, and service types. Next, we dive into the specific Azure services — starting with Azure’s global infrastructure.
Next up: Azure Regions, Zones, and Datacenters — where Azure physically lives around the world.