AZ-305 Design data storage solutions Practice Question
This AZ-305 practice question tests your understanding of design data storage solutions. 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.
Your company is designing a data storage solution for a global e-commerce platform. The solution must support high-frequency read and write operations with sub-millisecond latency, and must be able to handle schema-less JSON documents. Which Azure data service should you recommend?
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 guaranteed single-digit-millisecond latency for both reads and writes at the 99th percentile, making it ideal for high-frequency operations. It natively supports schema-less JSON documents through its SQL API, allowing flexible data models without requiring schema definitions or migrations.
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 SQL Database
Why it's wrong here
Azure SQL Database is relational and requires a fixed schema, not suitable for schema-less JSON.
✗
Azure Blob Storage
Why it's wrong here
Blob Storage is object storage for unstructured data, not optimized for low-latency document operations.
✓
Azure Cosmos DB
Why this is correct
Cosmos DB provides schema-less NoSQL storage with guaranteed sub-millisecond latency globally.
Related concept
Read the scenario before looking for a memorised answer.
✗
Azure Table Storage
Why it's wrong here
Table Storage is NoSQL but does not guarantee sub-millisecond latency and lacks advanced features.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Azure Table Storage's schema-less nature with Cosmos DB's capabilities, overlooking the critical requirement for sub-millisecond latency and global distribution that only Cosmos DB guarantees.
Detailed technical explanation
How to think about this question
Azure Cosmos DB achieves sub-millisecond latency through its indexing engine that automatically indexes all properties without requiring schema definitions, and its multi-region writes capability using the multi-master replication protocol. Under the hood, Cosmos DB uses a resource-governed, latch-free write-optimized engine and a B-tree-based index that supports point reads and queries with consistent low latency, even under high throughput. In a real-world e-commerce scenario, this allows the platform to handle millions of concurrent shopping cart updates and product catalog queries across global regions with strong consistency options.
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 AZ-305 question in full detail.
Design data storage solutions — This question tests Design data storage solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
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 guaranteed single-digit-millisecond latency for both reads and writes at the 99th percentile, making it ideal for high-frequency operations. It natively supports schema-less JSON documents through its SQL API, allowing flexible data models without requiring schema definitions or migrations.
What should I do if I get this AZ-305 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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