MS-900 Describe cloud concepts Practice Question
During requirements gathering, an IT manager says the organization must deploy application code without maintaining the operating system or runtime platform. Cloud concept or benefit best matches this requirement?
⚠ Common exam trap
Many exam-takers confuse PaaS with IaaS because both allow custom code deployment, but IaaS requires full OS and runtime management, which directly contradicts the requirement to avoid maintaining those layers.
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 choice because it provides a managed hosting environment where you can deploy your own application code without needing to manage the underlying operating system or runtime platform. The IT manager's requirement explicitly states they want to avoid maintaining the OS and runtime, which is the core value proposition of PaaS. In contrast, IaaS would require them to manage the OS and runtime themselves.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Private cloud
Why it's wrong here
Private cloud is a deployment model, not a service model, so it describes where the infrastructure lives (single-tenant, dedicated to one organization) rather than what management responsibilities are delegated. While a private cloud can provide more control or compliance, the IT manager would still need to procure, configure, and maintain an application platform or build one from scratch. Therefore it does not satisfy the requirement for a managed custom application environment and is incorrect here.
- ✓
Platform as a Service (PaaS)
Why this is correct
Platform as a Service (PaaS) is correct because it provides an integrated, managed hosting environment that includes the runtime, middleware, database, and underlying servers, allowing developers to focus exclusively on writing and deploying custom application code. The cloud provider handles operating system patching, scaling, and infrastructure maintenance, directly matching the requirement to build a custom app without managing the underlying platform. This is the service model that best fits the stated need.
- ✗
Infrastructure as a Service (IaaS)
Why it's wrong here
Infrastructure as a Service (IaaS) delivers raw virtualized compute, storage, and networking, but the customer retains responsibility for the operating system, runtime, middleware, and application itself. The IT manager's team would still need to provision VMs, install runtimes, configure the platform, and apply security patches, which defeats the goal of minimizing platform management. Since IaaS does not offload enough management responsibility to the provider, it is not the correct choice for a custom app platform.
- ✗
Software as a Service (SaaS)
Why it's wrong here
Software as a Service (SaaS) provides a fully finished, multi-tenant application—such as email or CRM—that is ready for end users and offers only limited configuration, not the ability to build a fundamentally custom line-of-business system. With SaaS, the IT manager would have to adapt business processes to the vendor's fixed feature set instead of coding a bespoke solution. Because the requirement is to create a custom application, SaaS is the wrong service model for this scenario.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
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