AZ-305 Design data storage solutions Practice Question
A company wants to analyze IoT sensor data from millions of devices in near real-time and store the raw data for batch processing. Which combination of Azure services should they use?
⚠ Common exam trap
Many candidates confuse Azure IoT Hub with Azure Event Hubs, assuming IoT Hub is required for all IoT scenarios, but Event Hubs is the correct choice for high-throughput, near real-time event ingestion without device management overhead.
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 Event Hubs and Azure Blob Storage
Azure Event Hubs is a highly scalable data streaming platform and event ingestion service capable of ingesting millions of events per second from IoT devices in near real-time. Azure Blob Storage provides cost-effective, durable object storage for the raw data, which can then be used for batch processing with services like Azure Data Lake Analytics or Azure Synapse. This combination directly meets the requirements for near real-time ingestion and raw data storage for batch processing.
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 Event Hubs and Azure Synapse Analytics
Why it's wrong here
Synapse Analytics is a distributed query and data warehousing engine, not a raw storage service; it analyzes data that has already been persisted elsewhere. Event Hubs efficiently ingests telemetry but requires a landing zone such as Blob Storage or Data Lake Storage to hold the raw payloads. Without that storage tier, the architectural pattern cannot capture or retain the original sensor data, so this pairing fails the stated requirement.
- ✗
Azure IoT Hub and Azure Cosmos DB
Why it's wrong here
Although IoT Hub offers device registration and bi-directional communication, its primary protocol and device management features add unnecessary complexity for pure telemetry ingestion compared to Event Hubs. Cosmos DB is a globally distributed, multi-model NoSQL database optimized for transactional and operational workloads, not for low-cost, high-volume raw data archival; its per-GB storage cost and indexing overhead make it unsuitable for millions of raw sensor records. Consequently, this combination neglects the need for a scalable, economical raw storage repository.
- ✗
Azure Data Lake Storage and Azure Stream Analytics
Why it's wrong here
Stream Analytics is a real-time data processing engine that consumes input from an event broker and can produce output to various sinks, but it does not itself receive or store massive streams; you still need an ingestion layer like Event Hubs to capture the raw events. Data Lake Storage is an excellent raw data store, yet pairing it solely with Stream Analytics leaves the critical ingestion path unresolved. The correct pattern places Event Hubs at the front to absorb the millions of IoT messages before routing them to storage.
- ✓
Azure Event Hubs and Azure Blob Storage
Why this is correct
Event Hubs is a fully managed, high-throughput event ingestion service that accepts millions of messages per second with low latency, making it ideal for collecting IoT telemetry. Blob Storage offers massively scalable, cost-effective object storage that preserves the raw event bodies exactly as received, providing a durable data lake foundation for subsequent analytical processing. Together they satisfy the core requirement of ingesting and storing raw sensor data before any transformation or querying.
Quick reference
Azure Blob Storage Tier Comparison
| Tier | Storage Cost | Retrieval Cost | Latency | Use Case |
|---|---|---|---|---|
| Hot | Highest | Lowest | Immediate | Active data, frequent reads |
| Cool | Lower | Higher | Immediate | Data accessed < once / month |
| Cold | Lower still | Higher | Immediate | Data accessed < once / quarter |
| Archive | Lowest | Highest + rehydration delay | Hours | Long-term compliance retention |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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