Quick Answer
Azure Cosmos DB is the correct choice because it delivers single-digit millisecond read and write latencies at global scale, perfectly matching the need to store IoT telemetry as small JSON payloads for real-time dashboards. Its multi-model, schema-agnostic design natively handles the write-once, read-frequently pattern of IoT data, while automatic indexing ensures dashboards query the latest telemetry without performance degradation. On the DP-900 exam, this scenario tests your ability to match workload characteristics—high-throughput writes, low-latency reads, and JSON format—to the appropriate Azure data store. A common trap is choosing Azure SQL Database or Azure Table Storage; SQL adds unnecessary relational overhead, and Table Storage lacks the sub-second read performance required for real-time dashboards. Remember the memory tip: “IoT telemetry dashboards need Cosmos DB’s speed—think ‘Cosmos for constant, low-latency streams.’”
This DP-900 practice question tests your understanding of describe considerations for working with non-relational data on azure. 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.
You are designing a solution to store IoT device telemetry data. Each message is a small JSON payload (1-2 KB). The data is written once and read frequently for real-time dashboards. Which Azure data store should you use?
Azure SQL Database
Why wrong: SQL Database is relational and may have overhead.
Azure Cosmos DB
Cosmos DB offers low-latency reads for JSON.
Azure Blob Storage
Why wrong: Blob Storage is not optimized for small, frequent reads.
Azure Table Storage
Why wrong: Table Storage is less suited for complex queries.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Azure Cosmos DB
Azure Cosmos DB is the correct choice because it is a globally distributed, multi-model database service that offers single-digit millisecond read and write latencies at any scale, making it ideal for real-time dashboards consuming IoT telemetry. Its support for JSON documents natively aligns with the small JSON payloads, and its ability to handle high-throughput writes (once) and low-latency reads (frequently) without schema management fits the workload perfectly.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Azure SQL Database
Why it's wrong here
SQL Database is relational and may have overhead.
Azure Cosmos DB
Why this is correct
Cosmos DB offers low-latency reads for JSON.
Related concept
Read the scenario before looking for a memorised answer.
Azure Blob Storage
Why it's wrong here
Blob Storage is not optimized for small, frequent reads.
Azure Table Storage
Why it's wrong here
Table Storage is less suited for complex queries.
Common exam traps
The trap here is that candidates often choose Azure Blob Storage because they associate 'JSON payloads' with 'files,' overlooking that Blob Storage lacks the low-latency query and indexing capabilities required for real-time dashboards, while Cosmos DB is purpose-built for such operational workloads.
Detailed technical explanation
Under the hood, Azure Cosmos DB uses a write-optimized, log-structured storage engine with automatic indexing of all fields by default, enabling efficient point reads and range queries without manual index tuning. For IoT scenarios, the change feed feature can stream real-time updates to dashboards or downstream processors, and the multi-master replication ensures global distribution with 99.999% availability. A subtle behavior is that Cosmos DB charges Request Units (RUs) per operation, so a high-frequency read workload on a dashboard may require careful RU provisioning to avoid throttling, unlike the fixed-cost models of Blob or Table Storage.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
What to study next
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FAQ
Describe considerations for working with non-relational data on Azure — This question tests Describe considerations for working with non-relational data on Azure — Read the scenario before looking for a memorised answer..
The correct answer is: Azure Cosmos DB — Azure Cosmos DB is the correct choice because it is a globally distributed, multi-model database service that offers single-digit millisecond read and write latencies at any scale, making it ideal for real-time dashboards consuming IoT telemetry. Its support for JSON documents natively aligns with the small JSON payloads, and its ability to handle high-throughput writes (once) and low-latency reads (frequently) without schema management fits the workload perfectly.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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