IaaS: Full Control Over Software Stack for Custom Libraries
A company develops a web application that relies on a custom library available only for a specific Linux distribution. They want to deploy the application in the cloud with minimal administrative overhead, but they need full control over the software stack, including the ability to install the custom library and configure the web server. Which cloud service model BEST meets these requirements?
Quick Answer
The answer is Infrastructure as a Service (IaaS). This is the correct choice because IaaS provides virtualized computing resources like virtual machines, giving you full control over the operating system, software stack, and configuration—exactly what you need to install a custom library tied to a specific Linux distribution and manually configure the web server. On the CompTIA A+ Core 1 220-1101 exam, this scenario tests your understanding of the IaaS vs PaaS vs SaaS cloud service models, where the key differentiator is control versus abstraction. A common trap is choosing PaaS, which handles the runtime environment and prevents OS-level customization, or SaaS, which offers no server access at all. Remember the memory tip: “IaaS gives you the keys to the car; PaaS gives you the driver’s seat; SaaS just gives you a ride.”
⚠ Common exam trap
CompTIA often tests the misconception that PaaS offers full control over the software stack because it allows deploying custom code, but in reality, PaaS restricts OS-level access and library installation, making IaaS the correct choice when distribution-specific dependencies are required.
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)
IaaS provides virtualized computing resources (e.g., virtual machines) over the internet, giving the company full control over the operating system, software stack, and configuration. This allows them to install the custom library specific to a Linux distribution and configure the web server as needed, while the cloud provider handles the underlying physical infrastructure, minimizing administrative overhead. SaaS, PaaS, and FaaS abstract away the underlying OS and runtime, preventing the installation of distribution-specific libraries or custom server configuration.
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 finished applications, so the provider controls the stack and customers cannot install a custom library or configure the web server. It is tempting for minimal administrative overhead, and would be correct if the requirement were simply consuming a vendor-hosted application.
- ✗
Platform as a Service (PaaS)
Why it's wrong here
PaaS abstracts the operating system and runtime, so the custom distribution-specific library cannot be installed or the web server configured directly. It is tempting because PaaS minimises administrative overhead for standard stacks, and would suit an application needing only supported runtimes and environment variables.
- ✓
Infrastructure as a Service (IaaS)
Why this is correct
Infrastructure as a Service delivers virtual machines where you control the operating system, so the distribution-specific custom library and web server configuration can be installed directly. It satisfies the stem's demand for full software stack control while the provider manages only the underlying hardware and hypervisor, keeping administrative overhead lower than on-premises.
- ✗
Function as a Service (FaaS)
Why it's wrong here
FaaS runs event-triggered code snippets on a managed runtime, so the provider fixes the OS and dependencies and no custom library or web server configuration is possible. It is tempting for minimal overhead, but would suit stateless functions rather than a full custom stack.
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 |
Go deeper
Related to this question
Learn chapter
Shared Responsibility Model
Key term
Software as a Service
Software as a Service (SaaS) is a cloud computing model where users access software applications over the internet on a subscription basis, without installing or maintaining the software locally.
Key term
Anything As A Service
A model where you rent any IT resource or service over the internet instead of owning it.
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Same concept, more angles
2 more ways this is tested on 220-1101
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 small business wants to develop and deploy a custom web application. They do not want to manage any underlying infrastructure, including servers, operating systems, or runtime environments. They want to simply upload their code and let the cloud provider handle scaling and maintenance. Which cloud service model BEST fits this requirement?
easy- A.Infrastructure as a Service (IaaS)
- ✓ B.Platform as a Service (PaaS)
- C.Software as a Service (SaaS)
- D.Anything as a Service (XaaS)
Why B: Platform as a Service (PaaS) is the correct choice because it provides a complete development and deployment environment in the cloud, abstracting away the underlying infrastructure. The business can upload custom code without managing servers, OS, or runtime, and the cloud provider automatically handles scaling, patching, and maintenance. This directly matches the requirement to avoid infrastructure management while deploying a custom web application.
Variation 2. A small business wants to deploy a customer relationship management (CRM) application for its sales team. The company wants to avoid managing servers, operating systems, or application patches. The sales team needs to access the CRM through a web browser from any device. The company prefers a monthly subscription model based on the number of users. Which cloud service model BEST fits these requirements?
medium- A.Infrastructure as a Service (IaaS)
- B.Platform as a Service (PaaS)
- ✓ C.Software as a Service (SaaS)
- D.Desktop as a Service (DaaS)
Why C: The company wants to avoid managing servers, operating systems, or application patches, and needs browser-based access with a monthly subscription per user. Software as a Service (SaaS) delivers a fully managed application over the internet, where the provider handles all infrastructure, platform, and software maintenance, exactly matching these requirements.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 practice question is part of Courseiva's free CompTIA 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 220-1101 exam.