AZ-900 Describe cloud concepts Practice Question
Which cloud service model gives customers the most control over the underlying infrastructure, including the operating system and networking?
⚠ Common exam trap
Many candidates confuse PaaS with IaaS because both involve virtual machines, but PaaS hides the OS and networking configuration, whereas IaaS grants full administrative access to 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
✓
Infrastructure as a Service (IaaS)
Infrastructure as a Service (IaaS) provides virtualized computing resources over the internet, giving customers direct control over the operating system, storage, and networking components such as virtual networks and firewalls. Unlike higher-level service models, IaaS allows users to manage and configure the underlying infrastructure without physical hardware access, making it the model with the most customer control.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Software as a Service (SaaS)
Why it's wrong here
SaaS delivers the entire application stack over the internet, and the provider manages everything from the underlying physical hardware through the operating system, middleware, and application code. The customer can only use the software via a subscription, with no ability to configure the OS or runtime environment. This yields the least customer control of the four options.
- ✗
Platform as a Service (PaaS)
Why it's wrong here
PaaS abstracts away the operating system, middleware, and infrastructure, presenting the customer with a managed hosting environment. The customer deploys only their own application and data, while the provider handles patching, scaling, and runtime maintenance. This leaves the customer with more control than SaaS or FaaS, but far less than IaaS, because the OS and runtime cannot be customized.
- ✓
Infrastructure as a Service (IaaS)
Why this is correct
Infrastructure as a Service provides the highest level of customer control because users rent raw compute, storage, and networking resources and then install, configure, and manage their own operating systems, middleware, and applications. The cloud provider is responsible only for the physical datacenter, virtualization, and network fabric. Customers can patch the OS, choose their own security settings, and deploy any software stack, making IaaS nearly equivalent to owning a physical server without the hardware maintenance burden.
- ✗
Function as a Service (FaaS)
Why it's wrong here
Function as a Service, or serverless computing, allows customers to upload individual code functions that run only when triggered by events, and the provider manages the servers, runtimes, and instance lifecycle entirely. The customer does not control the operating system, middleware, or even the execution environment—they control only the function's source code and configuration. This gives the customer less infrastructure control than PaaS and IaaS, although the function code itself remains customer-managed, unlike SaaS where the entire application is provider-owned.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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