Serverless vs PaaS vs IaaS decision in Azure - When to Use Which

The Big Idea

What if you could build apps without ever touching a server or worrying about updates?

The Scenario

Imagine you want to build a website or app. You try to set up everything yourself: buying servers, installing software, managing updates, and fixing problems. It feels like juggling many balls at once, and if one drops, your app breaks.

The Problem

Doing all this manually is slow and confusing. You spend more time fixing servers than building your app. Mistakes happen easily, like forgetting to update software or running out of space. This makes your app unreliable and hard to grow.

The Solution

Using Serverless, PaaS, or IaaS means the cloud provider handles much of the heavy lifting. You pick the right level of control and responsibility. Serverless lets you focus only on your code, PaaS gives you ready tools to build faster, and IaaS offers full control over virtual machines. This saves time and reduces errors.

Before vs After

✗ Before

Buy server -> Install OS -> Setup web server -> Deploy app -> Manage updates

✓ After

Choose Serverless or PaaS -> Upload code -> Cloud runs and scales automatically

What It Enables

You can build and grow apps quickly without worrying about managing servers or infrastructure details.

Real Life Example

A startup launches a new app using Serverless functions to handle user requests instantly, without buying or managing any servers, saving money and time.

Key Takeaways

Manual server management is slow and error-prone.

Serverless, PaaS, and IaaS offer different levels of control and ease.

Choosing the right option helps you focus on building your app, not managing infrastructure.

Practice

1. Which Azure service model lets you run your code without worrying about managing servers and charges you only when your code runs?

easy

A. Serverless

B. PaaS

C. IaaS

D. On-premises servers

Solution

1. Step 1: Understand Serverless model

   Serverless runs your code without managing servers and charges based on usage.

2. Step 2: Compare with PaaS and IaaS

   PaaS provides a platform but you still deploy apps; IaaS requires managing virtual machines.

3. Final Answer:

   Serverless -> Option A

4. Quick Check:

   Serverless = code runs without server management [OK]

Hint: Serverless = no server management, pay per execution [OK]

Common Mistakes:

• Confusing PaaS with Serverless
• Thinking IaaS is serverless
• Assuming on-premises is cloud

2. Which Azure service model requires you to manage virtual machines and network settings yourself?

easy

A. Serverless

B. SaaS

C. PaaS

D. IaaS

Solution

1. Step 1: Identify IaaS responsibilities

   IaaS gives full control over virtual machines and network settings, so you manage them.

2. Step 2: Contrast with other models

   Serverless and PaaS abstract server management; SaaS is software delivered fully managed.

3. Final Answer:

   IaaS -> Option D

4. Quick Check:

   IaaS = manage VMs and network [OK]

Hint: IaaS means managing your own virtual machines [OK]

Common Mistakes:

• Mixing PaaS with IaaS management level
• Thinking Serverless requires VM management
• Confusing SaaS with IaaS

3. You want to deploy a web app quickly without managing servers but need some control over the environment. Which Azure model fits best?

medium

A. Serverless

B. PaaS

C. IaaS

D. On-premises

Solution

1. Step 1: Analyze deployment needs

   Quick deployment without server management suggests Serverless or PaaS.

2. Step 2: Consider control over environment

   Serverless offers less control; PaaS provides a ready platform with some environment control.

3. Final Answer:

   PaaS -> Option B

4. Quick Check:

   PaaS = quick deploy + some control [OK]

Hint: PaaS balances ease and control for app deployment [OK]

Common Mistakes:

• Choosing Serverless when environment control is needed
• Picking IaaS for quick deployment
• Confusing on-premises with cloud models

4. A developer deployed an app on Azure IaaS but forgot to configure the network security group. What is the likely issue?

medium

A. App is exposed to the internet without protection

B. App will not run because code is missing

C. Azure automatically secures the app by default

D. App will run serverless without VMs

Solution

1. Step 1: Understand IaaS network responsibility

   In IaaS, you must configure network security groups to protect VMs and apps.

2. Step 2: Consequence of missing security group

   Without it, the app is exposed to the internet without firewall protection.

3. Final Answer:

   App is exposed to the internet without protection -> Option A

4. Quick Check:

   IaaS needs manual network security setup [OK]

Hint: IaaS needs manual network security setup [OK]

Common Mistakes:

• Assuming Azure auto-secures IaaS apps
• Thinking app won't run without code
• Confusing serverless with IaaS

5. Your company needs to run a batch job that runs only a few minutes every day, with minimal management and cost. Which Azure model should you choose?

hard

A. IaaS with dedicated VMs running 24/7

B. PaaS with always-on app service

C. Serverless functions triggered by schedule

D. On-premises servers scheduled manually

Solution

1. Step 1: Analyze job characteristics

   The batch job runs briefly daily, so paying for always-on resources wastes money.

2. Step 2: Match model to cost and management needs

   Serverless functions run only when triggered, minimizing cost and management.

3. Step 3: Eliminate other options

   IaaS and PaaS keep resources running continuously, increasing cost; on-premises adds manual overhead.

4. Final Answer:

   Serverless functions triggered by schedule -> Option C

5. Quick Check:

   Short, infrequent jobs = Serverless [OK]

Hint: Use serverless for short, infrequent tasks to save cost [OK]

Common Mistakes:

• Choosing always-on VMs for short jobs
• Picking PaaS without considering cost
• Ignoring serverless scheduling options