The answer is Azure Cosmos DB with Core (SQL) API. This is the correct choice because it natively stores semi-structured JSON documents, supports high-throughput writes with single-digit millisecond latency, and allows querying the data directly using standard SQL syntax, making it ideal for high-throughput JSON storage with SQL queries from IoT devices. On the DP-203 exam, this scenario tests your ability to match workload characteristics—specifically, the need for schema-agnostic ingestion of JSON logs and real-time queryability—to the appropriate Azure data store. A common trap is to choose Azure SQL Database or Azure Data Lake Storage, but those lack the native JSON indexing and guaranteed low-latency writes that Cosmos DB provides for IoT telemetry. Remember the memory tip: “JSON logs need Cosmos—SQL API for the query, high throughput for the stream.”
DP-203 Design and implement data storage Practice Question
This DP-203 practice question tests your understanding of design and implement data storage. 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 data engineer needs to store semi-structured JSON logs from IoT devices. The data will be queried using SQL and must support high-throughput writes. Which Azure data store is most appropriate?
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 with Core (SQL) API
Azure Cosmos DB with Core (SQL) API is the most appropriate choice because it natively stores semi-structured JSON documents, supports high-throughput writes with single-digit millisecond latency, and allows querying the JSON data directly using SQL syntax. Its schema-agnostic design and automatic indexing make it ideal for IoT workloads where device telemetry arrives at high velocity and must be immediately queryable.
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 Blob Storage with JSON blobs
Why it's wrong here
Unstructured storage, no native SQL querying.
✓
Azure Cosmos DB with Core (SQL) API
Why this is correct
Optimized for semi-structured JSON, native SQL API, and high-throughput writes.
Related concept
Read the scenario before looking for a memorised answer.
✗
Azure Data Lake Storage Gen2 with JSON files and PolyBase
Why it's wrong here
PolyBase is for querying, but high-throughput writes to files may cause contention.
✗
Azure SQL Database with JSON columns
Why it's wrong here
Supports JSON but not designed for high-throughput writes from IoT.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose Azure Blob Storage or Data Lake Storage because they associate JSON files with cheap storage, but they overlook the requirement for high-throughput writes and native SQL querying, which Cosmos DB uniquely satisfies among the options.
Detailed technical explanation
How to think about this question
Cosmos DB uses a resource-governed, multi-master replication model that distributes write operations across physical partitions, enabling it to handle millions of writes per second with predictable performance. Its indexing engine automatically indexes every property in the JSON document without requiring schema definitions, which allows SQL queries to efficiently filter and project fields even as the JSON structure evolves. In real-world IoT scenarios, this means device telemetry can be ingested directly as JSON documents and queried immediately for dashboards or alerts without any ETL or schema migration.
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 DP-203 question in full detail.
Design and implement data storage — This question tests Design and implement data storage — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Azure Cosmos DB with Core (SQL) API — Azure Cosmos DB with Core (SQL) API is the most appropriate choice because it natively stores semi-structured JSON documents, supports high-throughput writes with single-digit millisecond latency, and allows querying the JSON data directly using SQL syntax. Its schema-agnostic design and automatic indexing make it ideal for IoT workloads where device telemetry arrives at high velocity and must be immediately queryable.
What should I do if I get this DP-203 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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