Cloud service models (IaaS, PaaS, SaaS) in AWS - Step-by-Step Execution

Process Flow - Cloud service models (IaaS, PaaS, SaaS)

User Needs Cloud Resources

↓

IaaS

↓

More Control

↓

User Installs

↓

and Runs OS

This flow shows how a user chooses between IaaS, PaaS, and SaaS based on how much control and management they want over cloud resources.

Execution Sample

AWS

User selects service model:
if model == 'IaaS':
  user manages OS and network
elif model == 'PaaS':
  user manages apps only
else:
  user uses ready apps

This code shows decision steps for what the user manages depending on the cloud service model chosen.

Process Table

Step	User Choice	Managed by User	Managed by Cloud	Resulting Control Level
1	IaaS	OS, Network, Storage, Apps	Hardware, Virtualization	High
2	PaaS	Apps	OS, Network, Storage, Runtime	Medium
3	SaaS	None	Everything (Apps + Infrastructure)	Low
4	Exit	N/A	N/A	User finished choosing service model

💡 User finishes choosing cloud service model and understands management responsibilities.

Status Tracker

Variable	Start	After IaaS	After PaaS	After SaaS
Managed by User	None	OS, Network, Storage, Apps	Apps	None
Managed by Cloud	All	Hardware, Virtualization	OS, Network, Storage, Runtime	Everything
Control Level	None	High	Medium	Low

Key Moments - 2 Insights

Why does the user manage more in IaaS than in SaaS?

Because in IaaS, the cloud only provides hardware and virtualization, so the user must manage OS and apps (see execution_table step 1 vs step 3). In SaaS, the cloud manages everything.

What does PaaS let the user focus on?

PaaS lets the user focus on building and managing apps only, while the cloud manages OS and infrastructure (see execution_table step 2).

Visual Quiz - 3 Questions

Look at the execution_table, what does the user manage in PaaS?

A OS and Network

B Everything

C Apps only

D Nothing

💡 Hint

Check the 'Managed by User' column at step 2 in execution_table.

At which step does the user have the highest control level?

A Step 1 (IaaS)

B Step 2 (PaaS)

C Step 3 (SaaS)

D Step 4 (Exit)

💡 Hint

Look at the 'Control Level' column in execution_table.

If the user wants to avoid managing OS, which model should they choose?

A PaaS

B SaaS

C IaaS

D None

💡 Hint

See which model leaves OS management to the cloud in execution_table.

Concept Snapshot

Cloud Service Models:
IaaS: User manages OS, network, storage; cloud manages hardware.
PaaS: User manages apps; cloud manages OS and infrastructure.
SaaS: Cloud manages everything; user just uses apps.
Choose based on control vs ease of use.

Full Transcript

This visual execution shows how cloud service models differ by what the user manages versus what the cloud manages. IaaS gives the user the most control but requires managing OS and apps. PaaS reduces user management to apps only. SaaS requires no management from the user, as the cloud handles everything. The execution table traces these differences step-by-step, showing management responsibilities and control levels. Key moments clarify common confusions about who manages what. The quiz tests understanding by referencing the execution table and variable tracker.

Practice

1. Which cloud service model lets you rent virtual machines and storage but requires you to manage the operating system and applications 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 characteristics

   IaaS provides virtual machines and storage but leaves OS and app management to the user.

2. Step 2: Compare with other models

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

3. Final Answer:

   Infrastructure as a Service (IaaS) -> Option B

4. Quick Check:

   IaaS = Rent VMs + manage yourself [OK]

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

Common Mistakes:

• Confusing PaaS with IaaS
• Thinking SaaS includes server management
• Mixing FaaS with IaaS

2. Which of the following is the correct description of Platform as a Service (PaaS)?

easy

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

B. You use ready-made software online without installation.

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

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

Solution

1. Step 1: Identify PaaS features

   PaaS provides a platform to develop and run apps without handling server management.

2. Step 2: Eliminate other options

   Installing and managing software on rented virtual machines describes IaaS. Using ready-made software online without installation describes SaaS, and managing physical servers in your own data center is on-premises management.

3. Final Answer:

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

4. Quick Check:

   PaaS = platform for apps, no server management [OK]

Hint: PaaS = build apps, no server hassle [OK]

Common Mistakes:

• Confusing PaaS with SaaS
• Thinking PaaS requires server management
• Mixing on-premises with cloud models

3. You want to use an online email service without installing or managing any software. Which cloud model does this represent?

medium

A. Infrastructure as a Service (IaaS)

B. Platform as a Service (PaaS)

C. Software as a Service (SaaS)

D. Database as a Service (DBaaS)

Solution

1. Step 1: Understand SaaS usage

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

2. Step 2: Match the example

   Online email services like Gmail are classic SaaS examples.

3. Final Answer:

   Software as a Service (SaaS) -> Option C

4. Quick Check:

   SaaS = ready software online [OK]

Hint: SaaS = use software online, no install [OK]

Common Mistakes:

• Choosing IaaS or PaaS for software use
• Confusing DBaaS with SaaS
• Thinking SaaS requires software installation

4. A developer tries to deploy an app on a cloud platform but must manually install the operating system and runtime. Which cloud model is incorrectly used here?

medium

A. Platform as a Service (PaaS)

B. Infrastructure as a Service (IaaS)

C. Software as a Service (SaaS)

D. Network as a Service (NaaS)

Solution

1. Step 1: Understand PaaS expectations

   PaaS should handle OS and runtime installation automatically.

2. Step 2: Identify the error

   Manually installing OS means the platform is acting like IaaS, not PaaS.

3. Final Answer:

   Platform as a Service (PaaS) -> Option A

4. Quick Check:

   PaaS = no manual OS install [OK]

Hint: PaaS hides OS setup; manual means wrong model [OK]

Common Mistakes:

• Assuming manual install fits PaaS
• Confusing IaaS with PaaS
• Ignoring SaaS and NaaS differences

5. A startup wants to quickly launch a web app without managing servers but needs custom code and database control. Which cloud model should they choose and why?

hard

A. PaaS, because it lets them deploy code easily without server management.

B. IaaS, because it offers full control over servers and databases.

C. SaaS, because it provides ready-made apps with no coding needed.

D. On-premises, because cloud models don't allow custom code.

Solution

1. Step 1: Analyze startup needs

   They want no server management but need to run custom code and control databases.

2. Step 2: Match needs to cloud models

   IaaS requires server management, SaaS lacks custom code control, on-premises is not cloud.

3. Step 3: Confirm PaaS fit

   PaaS allows deploying custom code and managing databases without managing servers.

4. Final Answer:

   PaaS, because it lets them deploy code easily without server management. -> Option A

5. Quick Check:

   Custom code + no server management = PaaS [OK]

Hint: Custom code + no servers = PaaS [OK]

Common Mistakes:

• Choosing IaaS despite server management need
• Picking SaaS which lacks custom code control
• Thinking on-premises is cloud