AZ-900 Describe Azure architecture and services Practice Question

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 is a serverless compute service that scales to zero and executes code on triggers; it is not intended to host an always-on web tier, because it introduces cold starts and lacks persistent application state. Azure Cosmos DB is a multi-model NoSQL database with horizontal partitioning and wire protocols for MongoDB/Cassandra, not a relational engine, so it cannot replace a SQL database for ACID-heavy transaction processing in a traditional web app.

  When this WOULD be correct

  A company needs a serverless compute solution for event-driven workloads (e.g., processing IoT data) and a globally distributed NoSQL database for low-latency access. The question would specify event-driven scaling and NoSQL requirements.

• ✓

  Azure App Service and Azure SQL Database

  Why this is correct

  Azure App Service is a fully managed PaaS offering for web applications that provides automatic scaling, load balancing, and built-in DevOps capabilities without managing VMs. Azure SQL Database is a managed relational database with high availability, automated backups, and a compatibility level for typical transactional SQL workloads. Together they form a standard multi-tier stack where the web tier handles HTTP requests and the data tier stores structured data with low-latency access.

• ✗

  Azure Virtual Machine Scale Sets and Azure Files

  Why it's wrong here

  Azure Virtual Machine Scale Sets provide autoscaling for compute, but Azure Files offers shared file storage with latency unsuitable for transactional database workloads, which require low-latency block storage such as Azure SQL Database or managed disks. This combination tempts because Azure Files is a convenient shared storage for web-tier static content or application configuration, where throughput matters more than sub-millisecond I/O.

  When this WOULD be correct

  A company needs to run a legacy application with stateful VMs that require shared file storage across instances, and the database tier can use a separate VM with managed disks for performance. The question would emphasize lift-and-shift migration with minimal code changes.

• ✗

  Azure Kubernetes Service and Blob Storage

  Why it's wrong here

  Azure Kubernetes Service gives you managed Kubernetes orchestration but requires cluster management, autoscaling of pods, and more operational overhead than PaaS web hosting, making it heavier than necessary for a typical web tier. Blob Storage is object storage optimized for large amounts of unstructured data; it is accessed via REST and has higher latency per I/O than block-based database storage, so it is unsuitable for transactional workloads that require low-latency reads and writes. This pairing might be considered because AKS scales containers and Blob can hold static assets, but it does not provide a relational database tier.

  When this WOULD be correct

  A company needs to run containerized microservices with auto-scaling and store large amounts of unstructured data (e.g., images, videos) with high durability and low cost.

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.

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?”

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