AZ-900 Describe cloud concepts Practice Question
Which type of cloud service model would a company typically use for hosting their own custom web application where they manage the code but not the server operating system?
⚠ Common exam trap
A common mix-up: candidates confuse PaaS with IaaS because they think 'managing the code' implies full control over the server, but PaaS still abstracts the OS while IaaS requires OS management.
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
✓
PaaS (Platform as a Service)
PaaS (Platform as a Service) is correct because the company manages only the application code and data, while the cloud provider handles the underlying server operating system, runtime, middleware, and infrastructure. This aligns with the scenario where the customer controls the custom web application but not the OS.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
IaaS (Infrastructure as a Service)
Why it's wrong here
IaaS delivers virtualized computing resources like VMs, storage, and networks, but you remain responsible for patching the OS, installing runtimes, and configuring the web server. Azure App Service, by contrast, abstracts the entire hosting platform: you upload code and Azure provisions and manages the underlying IIS/OS, making IaaS a heavier operational burden than what PaaS offers for web app hosting.
- ✓
PaaS (Platform as a Service)
Why this is correct
PaaS provides a managed hosting platform, such as Azure App Service, where developers deploy custom application code without ever touching the OS, runtime, or web server. Azure handles patching, load balancing, and scaling automatically, so the developer focuses solely on the application logic. This matches the scenario's requirement to host a custom web app without managing server infrastructure, making PaaS the correct cloud service model.
- ✗
SaaS (Software as a Service)
Why it's wrong here
SaaS offers complete, ready-to-use software applications (like Office 365 or Salesforce) accessed over the internet, where users customize only configuration, not code. The scenario involves deploying a custom-built web app, not subscribing to an existing application. Thus, SaaS is incorrect because it does not let developers upload and run their own application code; PaaS is specifically designed for that purpose.
- ✗
FaaS (Function as a Service)
Why it's wrong here
FaaS, or serverless functions, executes discrete, event-driven code snippets (e.g., Azure Functions) that scale to zero and charge per execution. While a custom web app could theoretically be built with FaaS, the typical and expected model for full, always-running web applications is PaaS, especially using Azure App Service. PaaS provides a consistent hosting environment with built-in features for continuous deployment, staging slots, and WebJobs, which FaaS lacks for traditional request-response web apps.
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