The answer is Azure App Service and Azure SQL Database. This combination is correct because App Service offers built-in autoscaling based on metrics like CPU usage, allowing the web tier to scale out automatically as demand increases, while Azure SQL Database provides high-performance, low-latency transactional storage with features like automatic indexing and in-memory OLTP. On the AZ-900 exam, this question tests your understanding of matching platform-as-a-service (PaaS) solutions to specific workload requirements—a common scenario where candidates mistakenly pair a virtual machine scale set (VMSS) with Cosmos DB, forgetting that VMSS requires more manual configuration for scaling and Cosmos DB is optimized for NoSQL, not transactional relational data. The trap is assuming any scalable compute plus any database works; the key is recognizing that App Service handles web-tier autoscaling natively and SQL Database is built for ACID transactions. Memory tip: think “App + SQL” for “Auto-scale + SQL transactions”—two PaaS services that handle the heavy lifting for you.
AZ-900 Describe Azure architecture and services Practice Question
This AZ-900 practice question tests your understanding of describe azure architecture and services. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is designing a multi-tier application on Azure. The web tier needs to scale out based on CPU usage, while the database tier requires high-performance storage for transactional data. Which combination of Azure services should they choose?
Why wrong: Azure Functions can scale, but it's serverless, not typical for a web tier; Cosmos DB is a NoSQL database, not ideal for transactional SQL workloads.
B
Azure App Service and Azure SQL Database
App Service provides autoscaling for web applications, and Azure SQL Database offers high-performance transactional storage with built-in scaling.
C
Azure Virtual Machine Scale Sets and Azure Files
Why wrong: VMSS can scale, but managing VMs is more complex; Azure Files is a file share, not a transactional database.
D
Azure Kubernetes Service and Blob Storage
Why wrong: AKS is for containers; Blob Storage is object storage, not suitable for transactional workloads.
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
Azure App Service provides built-in autoscaling based on metrics like CPU usage, making it ideal for the web tier that needs to scale out. Azure SQL Database offers high-performance, low-latency storage for transactional data with features like automatic indexing and in-memory OLTP, meeting the database tier's requirements.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 Functions and Azure Cosmos DB
Why it's wrong here
Azure Functions can scale, but it's serverless, not typical for a web tier; Cosmos DB is a NoSQL database, not ideal for transactional SQL workloads.
✓
Azure App Service and Azure SQL Database
Why this is correct
App Service provides autoscaling for web applications, and Azure SQL Database offers high-performance transactional storage with built-in scaling.
Related concept
Read the scenario before looking for a memorised answer.
✗
Azure Virtual Machine Scale Sets and Azure Files
Why it's wrong here
VMSS can scale, but managing VMs is more complex; Azure Files is a file share, not a transactional database.
✗
Azure Kubernetes Service and Blob Storage
Why it's wrong here
AKS is for containers; Blob Storage is object storage, not suitable for transactional workloads.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Azure Functions with App Service for web tier scaling, overlooking that Functions is for event-driven, stateless code, not for a full web application with persistent scaling needs.
Detailed technical explanation
How to think about this question
Azure App Service's autoscaling uses Azure Monitor metrics and can scale out to multiple instances within seconds, supporting both horizontal and vertical scaling. Azure SQL Database's DTU or vCore-based purchasing models allow for predictable performance, and features like read replicas and geo-replication ensure high availability for transactional workloads. In a real-world scenario, a retail application might use App Service to handle fluctuating traffic during sales events while SQL Database processes order transactions with consistent low latency.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-900 question in full detail.
Describe Azure architecture and services — This question tests Describe Azure architecture and services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Azure App Service and Azure SQL Database — Azure App Service provides built-in autoscaling based on metrics like CPU usage, making it ideal for the web tier that needs to scale out. Azure SQL Database offers high-performance, low-latency storage for transactional data with features like automatic indexing and in-memory OLTP, meeting the database tier's requirements.
What should I do if I get this AZ-900 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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