AZ-900 Describe Azure architecture and services Practice Question
A company plans to migrate a multi-tier web application to Azure. The frontend web tier must automatically scale out based on CPU utilization, and Microsoft must manage the underlying virtual machines and operating system. The backend tier requires a relational database with built-in high availability and automatic backups. The company wants to minimize administrative overhead. Which two Azure services should the company use?
⚠ Common exam trap
Candidates often overlook the requirement that Microsoft must manage the underlying VMs and OS for the frontend. They may consider Azure Virtual Machine Scale Sets as a PaaS-like option, but the OS is still the customer's responsibility. The correct PaaS choice for web apps is Azure App Service.
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 App Service and Azure SQL Database
The frontend requires Microsoft-managed VMs and OS, which is a PaaS offering like Azure App Service. Azure App Service provides automatic scaling based on CPU utilization without managing underlying infrastructure. For the backend, a relational database with built-in high availability and automatic backups is best served by Azure SQL Database, which is fully managed with minimal administrative overhead. Option A (Azure Virtual Machines + Azure SQL Managed Instance) does not meet the requirement because Azure Virtual Machines is IaaS, where the customer manages the OS and VMs. Option C (AKS + Cosmos DB) involves managing Kubernetes clusters and Cosmos DB is NoSQL, not relational. Option D (Azure Functions + Table Storage) is serverless but not relational. Therefore, only option B satisfies both requirements.
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 Virtual Machines and Azure SQL Managed Instance
Why it's wrong here
Azure Virtual Machines provide IaaS where you manage the OS and applications, so it does not meet the requirement of Microsoft managing the underlying VMs and OS. Azure SQL Managed Instance is a managed database but the frontend tier fails the condition.
- ✓
Azure App Service and Azure SQL Database
Why this is correct
Azure App Service is a fully managed PaaS for web apps that supports autoscaling based on CPU utilization, and Microsoft manages the infrastructure. Azure SQL Database is a fully managed relational database with built-in HA and automatic backups, minimizing administrative overhead.
- ✗
Azure Kubernetes Service and Azure Cosmos DB
Why it's wrong here
Azure Kubernetes Service requires you to manage the cluster (though some management is provided, it is not fully managed like PaaS, and you still have to manage the OS for nodes. Azure Cosmos DB is a NoSQL database, not relational.
When this WOULD be correct
This option would be correct if the question required container orchestration for microservices, needed a globally distributed NoSQL database with multi-model support, and the company had DevOps expertise to manage Kubernetes clusters.
- ✗
Azure Functions and Azure Table Storage
Why it's wrong here
Azure Functions is serverless but not suitable for a multi-tier web app frontend with autoscaling based on CPU (it scales based on triggers, not CPU). Azure Table Storage is NoSQL, not relational.
When this WOULD be correct
A company needs to process events from a queue or blob storage with a pay-per-execution model, and requires a NoSQL key-value store for semi-structured data with low latency, while minimizing cost and operational overhead.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-900 exam frequently reuses these exact scenarios with slightly different constraints.
✓Azure App Service and Azure SQL DatabaseCorrect answer▾
Why this is correct
Azure App Service is a fully managed PaaS for web apps that supports autoscaling based on CPU utilization, and Microsoft manages the infrastructure. Azure SQL Database is a fully managed relational database with built-in HA and automatic backups, minimizing administrative overhead.
✗Azure Kubernetes Service and Azure Cosmos DBWrong answer — click to see why▾
Why this is wrong here
Azure Kubernetes Service (AKS) requires the company to manage container orchestration and does not fully offload VM management, while Azure Cosmos DB is a NoSQL database, not a relational database, failing the requirement for a relational backend with built-in high availability and automatic backups.
★ When this WOULD be the correct answer
This option would be correct if the question required container orchestration for microservices, needed a globally distributed NoSQL database with multi-model support, and the company had DevOps expertise to manage Kubernetes clusters.
Why candidates choose this
Candidates may confuse AKS as a fully managed service (it manages the control plane but not the worker nodes) and think Cosmos DB supports relational queries, overlooking the explicit relational database requirement.
✗Azure Functions and Azure Table StorageWrong answer — click to see why▾
Why this is wrong here
Azure Functions is a serverless compute service for event-driven workloads, not for a multi-tier web app requiring automatic scaling based on CPU utilization with managed VMs. Azure Table Storage is a NoSQL key-value store, not a relational database with built-in high availability and automatic backups.
★ When this WOULD be the correct answer
A company needs to process events from a queue or blob storage with a pay-per-execution model, and requires a NoSQL key-value store for semi-structured data with low latency, while minimizing cost and operational overhead.
Why candidates choose this
Candidates may think Azure Functions can handle the frontend scaling automatically (though it scales based on events, not CPU), and Azure Table Storage is a managed database, but they overlook the relational database requirement and the need for managed VMs in the frontend.
Analysis generated from the official AZ-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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
Learn chapter
Azure Regions and Geographies
Key term
Azure SQL Database
Azure SQL Database is a fully managed relational database-as-a-service (DBaaS) in Microsoft Azure, based on the SQL Server engine, that handles scaling, backups, patching, and high availability automatically.
Key term
Azure App Service
Azure App Service is a fully managed platform for building, deploying, and scaling web applications and APIs without managing the underlying infrastructure.
About these practice questions
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-900 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-900 exam.