AZ-204 Develop for Azure storage Practice Question
You are designing a solution that requires storing millions of small (1-5 KB) messages from IoT devices. Each message has a unique device ID and timestamp. You need to support efficient point queries by device ID and time range, and also support aggregation queries (e.g., count of messages per device per hour). Which Azure storage solution should you use?
⚠ Common exam trap
Many exam-takers choose Azure Cosmos DB for NoSQL because of its query flexibility and indexing, overlooking the cost implications and the fact that Azure Table Storage provides sufficient query capabilities for simple key-value and range queries at a fraction of the cost.
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 Table Storage
Azure Table Storage is the correct choice because it is a NoSQL key-value store optimized for storing large volumes of structured, non-relational data. It supports efficient point queries using the PartitionKey (device ID) and RowKey (timestamp), enabling fast retrieval by device ID and time range. Additionally, it allows aggregation queries like counting messages per device per hour via partition-scanned queries or client-side aggregation, and it is cost-effective for storing millions of small (1-5 KB) messages.
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 Cosmos DB for NoSQL
Why it's wrong here
Cosmos DB for NoSQL lacks native time-series optimisation, so point queries by device ID and timestamp require a custom partition key design that can lead to cross-partition scans, degrading performance at scale. Aggregation queries like per-device, per-hour counts would demand expensive change-feed processing or materialised views. It is tempting because its low-latency reads and flexible schema suit general IoT workloads, and it would be correct if the scenario required real-time updates, global distribution, or complex ad-hoc queries rather than high-throughput time-range and aggregation patterns.
- ✓
Azure Table Storage
Why this is correct
Azure Table Storage is a NoSQL key-value store highly optimized for storing massive amounts of structured, non-relational data, making it exceptionally cost-effective for small entities like IoT sensor readings. It provides highly efficient point queries using a composite PartitionKey and RowKey, which is ideal for retrieving specific device data by ID and timestamp. Its schema-less nature and scalability perfectly support millions of records for time-series data.
- ✗
Azure Queue Storage
Why it's wrong here
Azure Queue Storage is fundamentally designed for asynchronous messaging between decoupled application components, not for persistent, queryable data storage. Messages are transient, typically processed once, and then removed from the queue. It offers no indexing or direct query capabilities for historical data, making it entirely unsuitable for scenarios requiring retrieval of specific data points or aggregations based on device IDs and timestamps.
- ✗
Azure Blob Storage with JSON files
Why it's wrong here
Azure Blob Storage is optimized for storing large, unstructured binary data objects, such as documents, images, or log files. While it can store JSON files, it treats them as opaque blobs without internal indexing. Querying specific data points within these files, such as by device ID and timestamp, would necessitate downloading and parsing entire blobs, which is inefficient and costly for millions of small entities and frequent point queries.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-204 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-204 exam.