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.

• ✗

  Infrastructure as a Service (IaaS)

  Why it's wrong here

  Infrastructure as a Service (IaaS) gives you virtualized compute, storage, and networking on demand, but you must manage everything above the hardware: the guest operating system, middleware, runtime, security patches, and the accounting application itself. This is the opposite of a fully managed experience, because the customer retains significant administrative responsibility for the underlying stack. Since the question states that no management of the underlying resources is desired, IaaS is incorrect.

  When this WOULD be correct

  A company needs to deploy a custom application on virtual machines with full control over the OS, but wants to avoid managing physical hardware. They choose IaaS to provision VMs and handle OS configuration themselves.

• ✗

  Platform as a Service (PaaS)

  Why it's wrong here

  Platform as a Service (PaaS) provides an integrated hosting environment with managed operating systems, runtimes, and scaling, but it does not deliver a ready-to-use application. You still write, deploy, and maintain the application code, and you remain responsible for application-level configuration, security, and data. Because the user here wants to run an existing accounting application without any hands-on management, PaaS is not the right fit — it would still require your team to develop and manage the application itself.

  When this WOULD be correct

  A question where a company wants to develop and deploy a custom web application without managing the underlying OS, middleware, or runtime environment, but they still need to write and manage the application code. For example: 'A development team wants to host a custom web app without managing servers or OS, but they will write and maintain the application code.'

• ✓

  Software as a Service (SaaS)

  Why this is correct

  Software as a Service (SaaS) delivers a complete, production-ready application over the internet, typically through a web browser and a subscription or consumption-based license. The provider owns and operates the entire stack — networking, storage, servers, operating systems, middleware, runtime, data, and application code — so the tenant handles nothing more than user accounts, configuration, and business data. This matches the requirement to run an existing accounting application with no management of the underlying platform.

• ✗

  Functions as a Service (FaaS)

  Why it's wrong here

  Functions as a Service (FaaS) is a serverless computing model that executes individual units of code in response to events, with the platform handling automatic scaling and runtime environment provisioning. It is not a complete application delivery model: assembling a full accounting system would require many functions, orchestration, durable state, authentication, and integration logic that the user would still have to build and maintain. FaaS is therefore unsuitable as an answer because the objective is to consume a prebuilt application, not construct one from event-driven components.

  When this WOULD be correct

  A question that asks: 'A developer wants to run code in response to file uploads without provisioning servers. Which service model?' would make FaaS correct, as it focuses on event-driven, stateless functions.

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?”

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