IaaS: Customer Responsibilities for OS and Application Management
A company deploys a custom application on a cloud platform where they manage the operating system and runtime environment, but the cloud provider manages the underlying physical infrastructure, storage, and networking. Which cloud service model is being used?
Quick Answer
Infrastructure as a Service is the model being described because the dividing line in the scenario falls exactly where IaaS draws it: the customer manages the operating system and runtime, while the provider manages the physical hardware, storage, and networking beneath it. That split is the defining characteristic of IaaS across every cloud provider — the customer receives virtualised compute resources and takes on responsibility for everything from the OS upward, including patching, security configuration, and installed software, in exchange for the flexibility of full control over that layer. Contrast this with PaaS, where the provider also manages the OS and runtime and the customer works only with application code, or SaaS, where the customer manages nothing but data and user access. Recognising which layer the customer explicitly retains control over — OS and runtime here — is the fastest way to classify these service-model questions correctly, since the stem is deliberately built around that one boundary.
⚠ Common exam trap
Many exam-takers confuse IaaS with PaaS because both involve deploying applications, but the key differentiator is who manages the OS and runtime—IaaS gives the customer full control over these layers, whereas PaaS abstracts them away entirely.
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
✓
Infrastructure as a Service (IaaS)
The scenario describes a model where the customer manages the operating system and runtime environment, while the cloud provider handles the physical infrastructure, storage, and networking. This aligns precisely with Infrastructure as a Service (IaaS), as IaaS provides virtualized computing resources (e.g., virtual machines) where the customer retains control over the OS, middleware, and applications, but the provider manages the underlying hardware, hypervisor, and physical network.
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 this is correct
In IaaS, the customer has control over the operating system, storage, and deployed applications, while the provider manages the underlying infrastructure.
- ✗
Platform as a Service (PaaS)
Why it's wrong here
In PaaS, the provider manages the operating system and runtime; the customer only manages the application and data.
- ✗
Software as a Service (SaaS)
Why it's wrong here
In SaaS, the provider manages everything, and the customer only uses the application.
- ✗
Function as a Service (FaaS)
Why it's wrong here
FaaS is a serverless compute model where customers deploy functions without managing any underlying infrastructure or OS.
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Same concept, more angles
2 more ways this is tested on MS-900
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company runs a virtual machine in Azure that hosts a web application. The company is responsible for configuring the operating system, installing web server software, and managing application updates. The cloud provider is responsible for the physical hardware, networking, and data center security. Which cloud service model does this represent?
easy- A.Software as a Service (SaaS)
- B.Platform as a Service (PaaS)
- ✓ C.Infrastructure as a Service (IaaS)
- D.Function as a Service (FaaS)
Why C: This scenario describes Infrastructure as a Service (IaaS) because the customer manages the operating system, web server software, and application updates, while the cloud provider handles the physical hardware, networking, and data center security. In IaaS, the provider offers virtualized computing resources over the internet, and the customer retains control over the guest OS and installed software, which matches the responsibilities outlined.
Variation 2. A company runs a custom application on a cloud provider's infrastructure. The provider manages the physical servers, networking, and storage, but the company installs, configures, and patches the operating system and application. Which cloud service model is this?
medium- A.Software as a Service (SaaS)
- B.Platform as a Service (PaaS)
- ✓ C.Infrastructure as a Service (IaaS)
- D.Function as a Service (FaaS)
Why C: This scenario describes Infrastructure as a Service (IaaS) because the cloud provider manages the underlying physical infrastructure (servers, networking, storage), while the customer retains control over the operating system, middleware, and application. In IaaS, the customer is responsible for OS patching, configuration, and application management, which matches the given responsibilities.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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