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Guided AZ-900 Domain 1
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AZ-900 Study Guide

Domain 1: Describe Cloud Concepts

  • What is Cloud Computing? Free
  • Cloud Models: Public, Private, and Hybrid Free
  • Cloud Pricing: Consumption, Serverless, and Pay-as-You-Go Free
  • High Availability and Scalability Free
  • Reliability, Security, and Manageability Free
  • IaaS, PaaS, and SaaS Explained Free
  • Choosing the Right Cloud Service Free

Domain 2: Describe Azure Architecture and Services

  • Azure Regions, Zones, and Datacenters
  • Resources, Resource Groups, and Subscriptions
  • Azure Virtual Machines
  • Azure Compute: Containers, Functions, and App Service
  • Azure Networking: VNets, Subnets, and Peering
  • Connecting to Azure: VPNs, ExpressRoute, and DNS
  • Azure Storage Services
  • Data Migration: Moving to Azure
  • Microsoft Entra ID: Your Identity Hub
  • Authentication and External Identities
  • Azure Security: RBAC, Zero Trust, and Defender

Domain 3: Describe Azure Management and Governance

  • What Affects Your Azure Bill
  • Pricing Calculators: TCO and Azure Pricing
  • Cost Management and Tags
  • Azure Governance: Purview, Policy, and Locks
  • The Azure Portal and Cloud Shell
  • Infrastructure as Code: ARM, Bicep, and Arc
  • Azure Advisor and Service Health
  • Azure Monitor: Logs, Alerts, and Insights

AZ-900 Study Guide

Domain 1: Describe Cloud Concepts

  • What is Cloud Computing? Free
  • Cloud Models: Public, Private, and Hybrid Free
  • Cloud Pricing: Consumption, Serverless, and Pay-as-You-Go Free
  • High Availability and Scalability Free
  • Reliability, Security, and Manageability Free
  • IaaS, PaaS, and SaaS Explained Free
  • Choosing the Right Cloud Service Free

Domain 2: Describe Azure Architecture and Services

  • Azure Regions, Zones, and Datacenters
  • Resources, Resource Groups, and Subscriptions
  • Azure Virtual Machines
  • Azure Compute: Containers, Functions, and App Service
  • Azure Networking: VNets, Subnets, and Peering
  • Connecting to Azure: VPNs, ExpressRoute, and DNS
  • Azure Storage Services
  • Data Migration: Moving to Azure
  • Microsoft Entra ID: Your Identity Hub
  • Authentication and External Identities
  • Azure Security: RBAC, Zero Trust, and Defender

Domain 3: Describe Azure Management and Governance

  • What Affects Your Azure Bill
  • Pricing Calculators: TCO and Azure Pricing
  • Cost Management and Tags
  • Azure Governance: Purview, Policy, and Locks
  • The Azure Portal and Cloud Shell
  • Infrastructure as Code: ARM, Bicep, and Arc
  • Azure Advisor and Service Health
  • Azure Monitor: Logs, Alerts, and Insights
Domain 1: Describe Cloud Concepts Free ⏱ ~10 min read

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?

☕ Simple explanation

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.

Choosing between IaaS, PaaS, and SaaS depends on the workload requirements, the team’s technical capabilities, and the desired level of control:

IaaS when you need OS-level control, are migrating legacy applications (lift-and-shift), or require custom network configurations.

PaaS when your focus is application development, you want to reduce operational overhead, and the platform supports your application stack.

SaaS when you need a complete, pre-built application and don’t want to develop or maintain software yourself.

The decision framework

Scenario ClueService TypeWhy
”Legacy application,” “lift-and-shift,” “same OS”IaaSLegacy apps need specific OS configurations
”Full control over the operating system”IaaSOnly IaaS gives you OS access
”Custom network configuration”IaaSFine-grained networking requires IaaS
”Deploy code,” “focus on development”PaaSPaaS handles infrastructure so you focus on code
”Without managing servers”PaaSPaaS abstracts server management
”Managed database”PaaSAzure SQL Database, Cosmos DB = PaaS
”Ready-to-use application”SaaSSaaS = fully built software you subscribe to
”Email, collaboration, CRM”SaaSMicrosoft 365, Dynamics 365, Salesforce
”No development needed”SaaSIf 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.

ℹ️ 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:

  1. Year 1: Lift-and-shift legacy app to Azure VMs (IaaS)
  2. Year 2: Rebuild the app as a modern web app on Azure App Service (PaaS)
  3. 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

IaaSPaaSSaaS
Azure Virtual MachinesAzure App ServiceMicrosoft 365
Azure Virtual NetworkAzure SQL DatabaseDynamics 365
Azure Disk StorageAzure FunctionsPower BI (cloud)
Azure Load BalancerAzure Cosmos DBMicrosoft Intune
Network Security GroupsAzure Kubernetes ServiceOneDrive

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

🎬 Video coming soon

Choosing the Right Cloud Service — AZ-900

Choosing the Right Cloud Service — AZ-900

~8 min

Flashcards

Question

When should you choose IaaS?

Click or press Enter to reveal answer

Answer

When you need full OS control, are migrating legacy apps (lift-and-shift), require custom network configurations, or need to install specific software with custom settings.

Click to flip back
Question

When should you choose PaaS?

Click or press Enter to reveal answer

Answer

When you want to focus on developing and deploying code without managing infrastructure. Best for web apps, APIs, managed databases, and modern application development.

Click to flip back
Question

When should you choose SaaS?

Click or press Enter to reveal answer

Answer

When you need a ready-to-use application with no development required. Examples: email (Microsoft 365), CRM (Dynamics 365), collaboration tools.

Click to flip back

Knowledge Check

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?
Knowledge Check

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?
Knowledge CheckSelect all that apply

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.

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IaaS, PaaS, and SaaS Explained

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Azure Regions, Zones, and Datacenters

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