Cloud service models (IaaS, PaaS, SaaS) in Azure - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does IaaS stand for and what does it provide?

IaaS stands for Infrastructure as a Service. It provides virtual machines, storage, and networks that you can control and manage, like renting a computer in the cloud.

beginner

How is PaaS different from IaaS?

PaaS stands for Platform as a Service. It gives you a ready-to-use platform to build and run apps without managing the underlying servers or infrastructure.

beginner

What is SaaS and when do you use it?

SaaS means Software as a Service. It delivers ready-to-use software over the internet, like email or office apps, so you don’t have to install or manage anything.

intermediate

Which cloud service model lets you manage applications but not the servers?

PaaS lets you manage your applications and data but the cloud provider manages the servers and infrastructure.

intermediate

Match the cloud service model to its example: Azure Virtual Machines, Azure App Service, Microsoft 365.

Azure Virtual Machines = IaaS, Azure App Service = PaaS, Microsoft 365 = SaaS.

Which cloud model provides the most control over the operating system?

A All provide the same control

B PaaS

C SaaS

D IaaS

IaaS gives you virtual machines where you control the OS, unlike PaaS or SaaS.

Which service model is best when you want to focus only on using software without managing infrastructure?

A IaaS

B SaaS

C None of the above

D PaaS

SaaS delivers ready-to-use software, so you don’t manage infrastructure or platforms.

Azure App Service is an example of which cloud service model?

A PaaS

B IaaS

C SaaS

D None

Azure App Service provides a platform to deploy apps without managing servers, so it is PaaS.

Which cloud model requires you to manage the operating system and applications?

A IaaS

B PaaS

C SaaS

D All of them

In IaaS, you manage OS and apps; in PaaS and SaaS, the provider manages more layers.

Microsoft 365 is an example of which cloud service model?

A IaaS

B PaaS

C SaaS

D PaaS and SaaS

Microsoft 365 is software delivered over the internet, so it is SaaS.

Explain the main differences between IaaS, PaaS, and SaaS using a real-life analogy.

Think about what you manage and what the provider manages.

Describe a scenario where using PaaS would be better than IaaS or SaaS.

Focus on app development without infrastructure hassle.

Practice

1. Which cloud service model lets you rent virtual machines and manage the operating system yourself?

easy

A. Function as a Service (FaaS)

B. Infrastructure as a Service (IaaS)

C. Software as a Service (SaaS)

D. Platform as a Service (PaaS)

Solution

1. Step 1: Understand IaaS definition

   IaaS provides virtual machines and basic infrastructure, but you manage the OS and software.

2. Step 2: Compare with other models

   PaaS manages the platform, SaaS provides ready software, and FaaS is event-driven code execution.

3. Final Answer:

   Infrastructure as a Service (IaaS) -> Option B

4. Quick Check:

   IaaS = Rent VMs and manage OS [OK]

Hint: IaaS = rent machines, you manage OS and apps [OK]

Common Mistakes:

• Confusing PaaS with IaaS and thinking platform is managed by user
• Choosing SaaS thinking it includes VM management
• Selecting FaaS which is not a main cloud service model here

2. Which of the following is the correct description of PaaS?

easy

A. You install and manage software on rented virtual machines.

B. You manage physical servers in your own data center.

C. You use software online without installing it.

D. You use a platform to build and run apps without managing servers.

Solution

1. Step 1: Recall PaaS meaning

   PaaS provides a ready platform so you can build and run apps without handling server management.

2. Step 2: Eliminate other options

   You install and manage software on rented virtual machines. describes IaaS, C describes SaaS, and D is not cloud service but on-premises.

3. Final Answer:

   You use a platform to build and run apps without managing servers. -> Option D

4. Quick Check:

   PaaS = Platform managed, you build apps [OK]

Hint: PaaS = platform ready, no server management [OK]

Common Mistakes:

• Mixing PaaS with IaaS by thinking you manage servers
• Confusing SaaS with PaaS by thinking you build apps
• Choosing on-premises management as cloud service

3. You want to use Microsoft Azure to run a web app without managing the underlying servers. Which service model will you use?

medium

A. PaaS - Use Azure App Service to deploy your web app

B. IaaS - Create a virtual machine and install web server

C. SaaS - Use Microsoft Word online

D. IaaS - Rent storage only

Solution

1. Step 1: Identify requirement

   The user wants to run a web app without managing servers, so server management should be handled by provider.

2. Step 2: Match service model

   Azure App Service is a PaaS offering that lets you deploy apps without managing infrastructure.

3. Final Answer:

   PaaS - Use Azure App Service to deploy your web app -> Option A

4. Quick Check:

   Run app without servers = PaaS [OK]

Hint: Web app without servers means PaaS like Azure App Service [OK]

Common Mistakes:

• Choosing IaaS and thinking you don't manage servers
• Selecting SaaS which is for ready software, not custom apps
• Confusing storage rental with app hosting

4. A company wants to use cloud software without installing or managing it. They mistakenly choose IaaS and start managing virtual machines. What is the error?

medium

A. They should have chosen SaaS to avoid managing software.

B. IaaS automatically manages software for them.

C. PaaS requires installing software on VMs.

D. IaaS means software is fully managed by provider.

Solution

1. Step 1: Understand SaaS purpose

   SaaS provides ready-to-use software online without installation or management by user.

2. Step 2: Identify mistake with IaaS

   IaaS provides virtual machines but user must install and manage software themselves.

3. Final Answer:

   They should have chosen SaaS to avoid managing software. -> Option A

4. Quick Check:

   Want no software management = SaaS [OK]

Hint: No software management means SaaS, not IaaS [OK]

Common Mistakes:

• Thinking IaaS manages software automatically
• Confusing PaaS with SaaS in software management
• Believing IaaS means fully managed software

5. You want to build a custom business app that needs a database and automatic scaling but you don't want to manage servers or install software. Which Azure service model fits best?

hard

A. IaaS - Rent VMs and install database and app software yourself

B. SaaS - Use a ready-made business app online

C. PaaS - Use Azure SQL Database and Azure App Service

D. On-premises - Manage your own servers and software

Solution

1. Step 1: Analyze requirements

   Needs custom app, database, automatic scaling, no server or software management.

2. Step 2: Match with Azure services

   PaaS offers managed database (Azure SQL Database) and app hosting (Azure App Service) with scaling and no server management.

3. Step 3: Exclude other options

   IaaS requires managing servers and software, SaaS is not custom, on-premises is self-managed.

4. Final Answer:

   PaaS - Use Azure SQL Database and Azure App Service -> Option C

5. Quick Check:

   Custom app + no server management = PaaS [OK]

Hint: Custom app + no servers = PaaS with managed services [OK]

Common Mistakes:

• Choosing IaaS and expecting no server management
• Selecting SaaS expecting custom app building
• Thinking on-premises is cloud service