AZ-900 Describe cloud concepts Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  Software as a Service (SaaS)

  Why it's wrong here

  SaaS provides a fully functioning application, such as Microsoft 365 or Dynamics 365, that is managed end-to-end by the provider, covering the physical hardware, OS, application code, and data. The customer only configures user settings and data, with no ability to modify the underlying OS or infrastructure. For this question, SaaS is wrong because it gives only minimal user control and is not intended for developing or deploying custom code, even though it does let you avoid managing physical servers—the trade-off is that you lose infrastructure and runtime control entirely.

  When this WOULD be correct

  A question asking for a model where the provider manages everything and the customer only uses the application, such as 'Which cloud service model requires the least management effort from the customer?'

• ✗

  Platform as a Service (PaaS)

  Why it's wrong here

  PaaS, like Azure App Service, abstracts the OS and the runtime environment, so you simply deploy your code and the platform handles patching, load balancing, and scaling. The provider automates the entire underlying infrastructure, but you still retain control over your application's configuration and deployment. PaaS is wrong here because it restricts access to the OS and disallows installing arbitrary system-level components, making it unsuitable if you need to manage a virtual machine or customize the host environment; it is designed for developers who focus on code, not on infrastructure control.

  When this WOULD be correct

  A company wants to develop and deploy a web application without managing the underlying OS, runtime, or scaling. They need a fully managed environment to focus solely on code. In that case, PaaS is the correct choice.

• ✓

  Infrastructure as a Service (IaaS)

  Why this is correct

  Azure IaaS delivers virtualized compute, storage, and networking, with the cloud provider owning and maintaining the physical servers, power, cooling, and hardware lifecycle. The customer gains full control over the guest OS, middleware, and applications, allowing custom configurations and software installations. This means you avoid managing physical servers entirely—there is no rack mounting or hardware replacement—yet you still need to patch the OS and manage the application stack, which is what makes IaaS distinct for accommodating development workloads that require control. In this context, IaaS is correct because it completely abstracts the hardware layer while permitting the level of control needed to deploy a custom environment.

• ✗

  Functions as a Service (FaaS)

  Why it's wrong here

  FaaS (Azure Functions) runs event-driven code in ephemeral containers, where the provider manages all the physical and virtual infrastructure, including the runtime and scaling, and you are only charged for actual executions. You cannot log into an underlying OS, install software, or manage the server in any way because the compute is abstracted into on-demand functions. FaaS is wrong for this requirement because it offers no control over the OS or environment, which is the opposite of what is needed when you want to avoid physical servers but still have infrastructure-level decision-making and full server management.

  When this WOULD be correct

  A question asking which service model allows developers to run code in response to events without managing servers or runtime environments, focusing solely on code execution, would make FaaS correct.

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-900 exam frequently reuses these exact scenarios with slightly different constraints.

Analysis generated from the official AZ-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”