AZ-900 Describe cloud concepts Practice Question
A startup wants to run a web application without managing the underlying servers. They only want to upload their code and let the cloud provider handle the runtime, scaling, and maintenance. Which cloud service model is this?
⚠ Common exam trap
Test-takers frequently confuse PaaS with FaaS because both are 'serverless' in marketing, but FaaS (e.g., Azure Functions) is event-driven and stateless per invocation, not designed for a persistent web application with session state or long-running requests.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Platform as a Service (PaaS)
Platform as a Service (PaaS) is the correct model because it provides a managed hosting environment where the startup can deploy their web application code without managing the underlying servers, operating systems, or runtime infrastructure. Azure App Service is a prime example of PaaS, handling automatic scaling, patching, and load balancing while the customer only focuses on code and data.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Platform as a Service (PaaS)
Why this is correct
Platform as a Service (PaaS) provides a managed hosting environment that abstracts the underlying servers, operating systems, and runtime components. You deploy your web application code directly, and the provider automatically handles capacity provisioning, patching, and load balancing. This lets you focus on application logic while the platform manages the infrastructure, matching the requirement of running a web app without managing servers.
- ✗
Infrastructure as a Service (IaaS)
Why it's wrong here
Infrastructure as a Service (IaaS) provides virtualized compute, storage, and networking resources on demand, but you are responsible for provisioning and managing the virtual machines, operating systems, and middleware. You must handle OS updates, security patches, and application runtime configuration, meaning server management is still on your plate. Thus, IaaS does not meet the 'without managing servers' criterion.
When this WOULD be correct
A company needs to migrate an on-premises application to the cloud and requires full control over the operating system, middleware, and runtime environment, while still benefiting from scalable infrastructure. They would choose IaaS to manage these components themselves.
- ✗
Software as a Service (SaaS)
Why it's wrong here
Software as a Service (SaaS) delivers a fully functional, ready-to-use application over the internet, such as Office 365 or Salesforce. You do not deploy custom code; instead, you configure and use the vendor-provided software. Since the requirement is to run your own web application, SaaS does not apply because it offers no custom code deployment or runtime control.
When this WOULD be correct
A question that asks: 'A company wants to use a cloud-based email service without managing the underlying infrastructure or software. Which service model?' would make SaaS correct.
- ✗
Function as a Service (FaaS)
Why it's wrong here
Function as a Service (FaaS), exemplified by AWS Lambda, executes individual, event-triggered functions that are charged per invocation and scale automatically. It is not intended for full web applications with persistent sessions, long-running processes, or HTTP routing because each function is stateless and time-limited. Deploying a web app would require orchestrating multiple functions and external services, so FaaS is not the appropriate model.
When this WOULD be correct
A question like: 'A company needs to execute code in response to events (e.g., file uploads) without provisioning servers. Which service model?' — here FaaS is correct because it focuses on event-driven, stateless functions rather than a full application.
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.
✓Platform as a Service (PaaS)Correct answer▾
Why this is correct
Platform as a Service (PaaS) provides a managed hosting environment that abstracts the underlying servers, operating systems, and runtime components. You deploy your web application code directly, and the provider automatically handles capacity provisioning, patching, and load balancing. This lets you focus on application logic while the platform manages the infrastructure, matching the requirement of running a web app without managing servers.
✗Infrastructure as a Service (IaaS)Wrong answer — click to see why▾
Why this is wrong here
IaaS provides virtualized computing resources like VMs and storage, but the user must manage the OS, runtime, and scaling. The question specifies the startup wants to avoid managing servers and only upload code, which is not possible with IaaS.
★ When this WOULD be the correct answer
A company needs to migrate an on-premises application to the cloud and requires full control over the operating system, middleware, and runtime environment, while still benefiting from scalable infrastructure. They would choose IaaS to manage these components themselves.
Why candidates choose this
Candidates may confuse IaaS with PaaS because both involve cloud hosting, but IaaS still requires server management, which the question explicitly wants to avoid.
✗Software as a Service (SaaS)Wrong answer — click to see why▾
Why this is wrong here
SaaS delivers fully functional software applications over the internet, not a platform for deploying custom code. The startup wants to upload their own code, which is not supported by SaaS.
★ When this WOULD be the correct answer
A question that asks: 'A company wants to use a cloud-based email service without managing the underlying infrastructure or software. Which service model?' would make SaaS correct.
Why candidates choose this
Candidates may confuse 'not managing servers' with 'not managing any software,' overlooking that SaaS provides complete applications, not a runtime for custom code.
✗Function as a Service (FaaS)Wrong answer — click to see why▾
Why this is wrong here
FaaS (e.g., Azure Functions) is a subset of serverless computing where you deploy individual functions triggered by events, not a full web application. The question specifies running a web application and uploading code, which aligns with PaaS (e.g., Azure App Service) that handles the entire runtime and scaling without managing servers.
★ When this WOULD be the correct answer
A question like: 'A company needs to execute code in response to events (e.g., file uploads) without provisioning servers. Which service model?' — here FaaS is correct because it focuses on event-driven, stateless functions rather than a full application.
Why candidates choose this
Candidates confuse 'not managing servers' with serverless computing. FaaS is a serverless model, but the question asks about running a web application, not individual functions, making PaaS the appropriate choice.
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?”
Go deeper
Related to this question
Learn chapter
What is Cloud Computing?
Key term
PaaS
Platform as a Service (PaaS) is a cloud computing model that provides a managed platform for developers to build, run, and manage applications without dealing with the underlying infrastructure.
Key term
Environment
An environment is a dedicated set of computing resources, configurations, and services used to develop, test, or host software applications in a controlled and repeatable way.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-900 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-900 exam.