The correct approach is to use Azure Cosmos DB for transactional data and Azure Blob Storage for historical data. This combination directly satisfies the dual requirements because Cosmos DB delivers single-digit millisecond latency for transactional workloads, easily meeting the under-10ms query requirement, while Blob Storage provides massively lower-cost storage for large volumes of historical data that do not need real-time access. On the DP-203 exam, this scenario tests your ability to match workload characteristics to the right Azure service, often appearing in design questions about mixed workloads and cost optimization. A common trap is to default to a single service like Azure SQL Database or Synapse for everything, which would either fail the latency requirement or inflate storage costs. Remember the memory tip: "Hot transactions in Cosmos, cold history in Blobs" — think of Cosmos as the fast lane for live operations and Blob Storage as the cheap warehouse for archived data.
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.
You are designing a data storage solution for a retail company. The data includes transactional data that requires low-latency queries (under 10 milliseconds) and large historical data for analytics. The solution must minimize storage costs. Which approach should you recommend?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use Azure Cosmos DB for transactional data and Azure Blob Storage for historical data
Azure Cosmos DB provides single-digit millisecond latency for transactional workloads, meeting the under-10ms requirement, while Azure Blob Storage offers low-cost storage for large historical data. This combination minimizes storage costs by using the most cost-effective service for each workload type.
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.
✗
Use Azure Data Lake Storage Gen2 for both transactional and historical data
Why it's wrong here
Data Lake Storage is optimized for analytics, not low-latency transactions.
✗
Use Azure Cache for Redis for transactional data and Azure SQL Database for historical data
Why it's wrong here
Redis is a cache, not a durable data store; it cannot replace a transactional database.
✓
Use Azure Cosmos DB for transactional data and Azure Blob Storage for historical data
Why this is correct
Cosmos DB offers low-latency reads/writes, and Blob Storage is cheap for bulk historical data.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use Azure SQL Database with Hyperscale tier for both transactional and historical data
Why it's wrong here
Hyperscale is for large databases but not guaranteed sub-10ms latency for transactions.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may assume a single service like Azure SQL Database or Data Lake Storage can handle both transactional and analytical workloads efficiently, overlooking the cost and performance trade-offs that make a hybrid approach optimal.
Detailed technical explanation
How to think about this question
Azure Cosmos DB uses a multi-model, globally distributed database with automatic indexing and tunable consistency levels to achieve consistent single-digit millisecond latencies at the 99th percentile. Azure Blob Storage stores data as objects in a flat namespace, offering tiered storage (hot, cool, archive) to further reduce costs for infrequently accessed historical data. In a real-world scenario, a retail company might use Cosmos DB for real-time order processing and Blob Storage for storing years of sales logs, with Azure Data Factory orchestrating periodic data movement.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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: Use Azure Cosmos DB for transactional data and Azure Blob Storage for historical data — Azure Cosmos DB provides single-digit millisecond latency for transactional workloads, meeting the under-10ms requirement, while Azure Blob Storage offers low-cost storage for large historical data. This combination minimizes storage costs by using the most cost-effective service for each workload type.
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.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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