Serverless vs PaaS vs IaaS decision in Azure - Practice Questions

Challenge - 5 Problems

🧠 Conceptual

intermediate

Choosing the best Azure service model for a simple event-driven app

You want to build a small app that runs code only when a user uploads a file. You want to pay only when the code runs and avoid managing servers.

Which Azure service model fits best?

A Azure Blob Storage because it stores files but does not run code.

B Azure Virtual Machines (IaaS) because you get full control over the server and can install any software.

C Azure App Service (PaaS) because it automatically scales but you pay for reserved compute even if idle.

D Azure Functions (Serverless) because it runs code on demand and you pay per execution.

💡 Hint

Think about paying only when code runs and not managing servers.

Azure Functions is serverless, so it runs code only when triggered and charges per execution. This fits event-driven apps well.

❓ Architecture

intermediate

Selecting Azure service model for a web app needing custom OS configuration

You need to deploy a web app that requires installing custom OS software and full control over the environment.

Which Azure service model should you choose?

A Azure App Service (PaaS) because it manages OS and runtime for you.

B Azure Functions (Serverless) because it automatically scales without OS management.

C Azure Virtual Machines (IaaS) because it gives full control over OS and software installation.

D Azure Logic Apps because it is for workflow automation, not custom OS control.

💡 Hint

Think about needing full OS control and custom software installation.

Azure Virtual Machines provide full control over the OS and installed software, suitable for custom configurations.

✅ Best Practice

advanced

Cost optimization for a continuously running web app with moderate traffic

You have a web app that runs 24/7 with moderate traffic. You want to minimize management overhead and optimize cost.

Which Azure service model is the best choice?

A Azure App Service (PaaS) to reduce management overhead and pay for reserved compute.

B Azure Virtual Machines (IaaS) to control costs by managing VM size and uptime.

C Azure Functions (Serverless) because it charges only when code runs, ideal for continuous apps.

D Azure Container Instances because they are for short-lived containers, not continuous apps.

💡 Hint

Consider a service that reduces management but supports continuous running.

Azure App Service is PaaS that manages infrastructure and supports continuous apps with moderate traffic, balancing cost and management.

❓ security

advanced

Security responsibility in Azure service models

Which Azure service model requires you to manage the most security responsibilities, including OS patching and network configuration?

A Azure Virtual Machines (IaaS) because you manage OS, network, and app security.

B Azure App Service (PaaS) because you manage app security but not OS patching.

C Azure Functions (Serverless) because you manage code security only.

D Azure SQL Database (PaaS) because Microsoft manages OS and database security.

💡 Hint

Think about who manages OS and network security in each model.

In IaaS, you manage OS patching, network settings, and app security. PaaS and Serverless offload OS and infrastructure security to Azure.

❓ service_behavior

expert

Behavior of Azure Functions under heavy load

You deploy an Azure Function with a consumption plan. What happens when many events trigger the function simultaneously?

A Azure Functions queue the events and process them one by one on a single instance.

B Azure Functions automatically scale out by creating more instances to handle the load.

C Azure Functions reject new events until the current instance finishes processing all events.

D Azure Functions require manual scaling to handle increased load.

💡 Hint

Think about serverless scaling behavior on demand.

Azure Functions on a consumption plan automatically scale out by adding instances to handle many simultaneous events.

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