AZ-900 Exam Cram: Cloud Service Types

This guide focuses on the fundamental cloud service models (IaaS, PaaS, SaaS) and the Shared Responsibility Model, essential for the Microsoft Azure Fundamentals (AZ-900) exam.

Topic Weighting

[!IMPORTANT] Expect at least 3-5 questions directly mapping specific Azure services (like VMs or App Services) to their respective service type (IaaS, PaaS, or SaaS).

Key Concepts Summary

1. Infrastructure as a Service (IaaS)

• Definition: The most flexible category. You rent hardware (servers, VMs, storage, networks) from a cloud provider.
• Responsibility: You are responsible for the OS, middleware, and data. The provider manages the physical hardware.
• Use Case: Migrating existing applications (Lift-and-Shift), testing/development environments.

2. Platform as a Service (PaaS)

• Definition: Provides a framework for building, testing, and deploying apps without managing underlying infrastructure.
• Responsibility: Provider manages the OS, patches, and runtime. You manage the application code and data.
• Use Case: Web application development, API management, Analytics.

3. Software as a Service (SaaS)

• Definition: Software hosted centrally and managed by the provider. Usually accessed via a web browser.
• Responsibility: Provider manages everything. You simply use the software.
• Use Case: Email (Outlook), Productivity (Office 365), CRM (Salesforce).

Visualizing Choice

Common Pitfalls

• The OS Trap: Many students think PaaS involves managing the Operating System. Wrong. In PaaS, the cloud provider handles OS updates and patching.
• Responsibility Confusion: A common exam question asks who is responsible for data. Answer: In EVERY model (IaaS, PaaS, SaaS, and On-Prem), the customer is always responsible for their data and identities.
• Serverless vs. PaaS: Serverless (like Azure Functions) is often considered a sub-type of PaaS where scaling is automatic and you pay only for execution time.

Mnemonics / Memory Triggers

• IaaS = I-Manage: You manage the virtual hardware and OS.
• PaaS = Platform for Developers: You focus on the code; the platform handles the rest.
• SaaS = Software for Users: You just log in and use it.

[!TIP] Think of the "Pizza as a Service" analogy:

• On-Prem: Homemade pizza (You do everything).
• IaaS: Take-and-Bake (They provide the pizza, you provide the oven and table).
• PaaS: Pizza Delivery (They cook it; you provide the table and drinks).
• SaaS: Dining Out (They do everything; you just eat).

Formula / Equation Sheet

Shared Responsibility Matrix

Comparison Table

Practice Set

Q1: Which cloud service type is most suitable for a "Lift-and-Shift" migration where you want to move a server to the cloud exactly as it is?

• Answer: IaaS. It provides the virtualized hardware that mimics on-premises servers.

Q2: You are developing a new web application and want to focus on coding without worrying about the underlying web server software or OS updates. Which model should you use?

• Answer: PaaS. It abstracts the infrastructure so you can focus on deployment.

Q3: True or False: In a SaaS model, the customer is responsible for managing the security of the physical data center.

• Answer: False. The cloud provider is always responsible for physical security in any cloud model.

Q4: Which cloud service model typically uses a subscription-based pricing model where you pay for access to a finished product?

• Answer: SaaS (e.g., Microsoft 365).

Q5: Who is responsible for securing the data stored in a PaaS solution?

• Answer: The Customer. Responsibility for data always remains with the customer across all cloud models.**