AZ-900 Describe Azure architecture and services Practice Question
A developer needs to create a serverless API that executes code in response to HTTP requests without managing any server infrastructure. Which Azure service is BEST suited?
⚠ Common exam trap
Watch out — candidates often confuse Azure App Service (PaaS) with serverless, but App Service still requires managing an app service plan and does not provide the same granular, event-driven scaling and pay-per-execution model as Azure Functions.
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
✓
Azure Functions
Azure Functions is the correct choice because it is a serverless compute service that allows you to run event-driven code without provisioning or managing infrastructure. It natively supports HTTP triggers, enabling the creation of RESTful APIs that execute code in response to HTTP requests, and scales automatically based on demand.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Azure App Service
Why it's wrong here
Azure App Service lets you deploy web apps without managing the OS, but you must explicitly choose an App Service Plan, which is a pre-provisioned set of virtual machines with fixed resource limits. The plan runs continuously, so you pay for idle capacity, and you are responsible for configuring autoscaling and choosing the correct SKU. This is platform-as-a-service, not serverless.
- ✓
Azure Functions
Why this is correct
Azure Functions on the Consumption plan is serverless: HTTP-triggered functions scale automatically on demand, and you pay only for execution time and resources used. The platform manages all infrastructure including the runtime host, and there is no server to provision, patch, or scale manually. This makes it the best fit for event-driven code triggered by an HTTP request.
- ✗
Azure Kubernetes Service
Why it's wrong here
Azure Kubernetes Service is a managed Kubernetes platform, but it is not serverless. You must design, operate, and scale node pools, which are virtual machines, and handle Kubernetes version upgrades, monitoring, and workload scheduling. For a simple HTTP-triggered task, this is far more infrastructure overhead than needed.
- ✗
Azure Virtual Machines
Why it's wrong here
Azure Virtual Machines give you full control over the operating system, but that means you are fully responsible for OS patching, security hardening, capacity planning, and scaling. You must either manually manage VMs or invest in VM scale sets and load balancing. This is the antithesis of serverless, where the platform hides all infrastructure.
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
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Azure Regions and Geographies
Key term
Azure Functions
Azure Functions is a serverless compute service that lets you run event-driven code without managing infrastructure, automatically scaling to meet demand.
Key term
Serverless
Serverless is a cloud computing model where the cloud provider manages the servers, and you only pay for the actual compute time your code uses, without having to worry about provisioning or maintaining infrastructure.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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