The correct choice is Azure Data Lake Storage Gen2 with Azure Synapse SQL pool. This combination is purpose-built for petabyte-scale analytics because ADLS Gen2 offers a hierarchical namespace and massive append-only storage, while Synapse SQL pool provides columnar storage via PolyBase or CETAS, enabling fast SQL-based querying on IoT telemetry data that is rarely updated. On the Microsoft Azure Solutions Architect Expert AZ-305 exam, this scenario tests your understanding of how to pair storage and compute for big data workloads, often appearing as a trap where candidates mistakenly choose Azure SQL Database or Cosmos DB, which lack native columnar optimization for append-only patterns. Remember the memory tip: “Append-only needs ADLS; columnar queries need Synapse SQL pool.”
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.
A company needs to store and analyze petabytes of IoT telemetry data. The data is append-only and rarely updated. They require SQL-based querying and columnar storage for fast analytics. Which Azure storage solution should you choose?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Azure Data Lake Storage Gen2 with Azure Synapse SQL pool
Azure Data Lake Storage Gen2 (ADLS Gen2) provides hierarchical namespace and petabyte-scale storage optimized for big data analytics. When combined with Azure Synapse SQL pool (formerly SQL DW), it enables SQL-based querying over columnar storage (using PolyBase or CETAS) for fast analytics on append-only IoT telemetry data. This combination supports massive data volumes, append-only workloads, and columnar storage for high-performance analytical queries.
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 Cosmos DB with analytical store
Why it's wrong here
Cosmos DB is for NoSQL and not optimized for append-only telemetry.
✗
Azure SQL Database with columnstore indexes
Why it's wrong here
Azure SQL Database is not designed for petabyte-scale append-only data.
✗
Azure Blob Storage with Azure Cognitive Search
Why it's wrong here
Blob Storage lacks native SQL querying for analytics.
✓
Azure Data Lake Storage Gen2 with Azure Synapse SQL pool
Why this is correct
Data Lake Storage Gen2 provides scalable storage and Synapse SQL pool enables SQL over Parquet.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose Azure SQL Database with columnstore indexes (Option B) because they focus on the 'SQL-based querying and columnar storage' requirement without considering the petabyte-scale constraint, which exceeds Azure SQL Database's maximum storage capacity.
Detailed technical explanation
How to think about this question
ADLS Gen2 uses a hierarchical namespace that enables POSIX-like access control and directory operations, while Azure Synapse SQL pool leverages massively parallel processing (MPP) architecture with distributed columnar storage (using clustered columnstore indexes by default) to achieve query performance on petabytes of data. The append-only nature of IoT telemetry aligns well with columnar storage because data is rarely updated, minimizing row-group fragmentation and maintaining high compression ratios. In real-world scenarios, this setup is commonly used for time-series analytics where data is ingested via Azure Event Hubs or IoT Hub into ADLS Gen2 and queried using Synapse SQL or serverless SQL pools.
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 Data Lake Storage Gen2 with Azure Synapse SQL pool — Azure Data Lake Storage Gen2 (ADLS Gen2) provides hierarchical namespace and petabyte-scale storage optimized for big data analytics. When combined with Azure Synapse SQL pool (formerly SQL DW), it enables SQL-based querying over columnar storage (using PolyBase or CETAS) for fast analytics on append-only IoT telemetry data. This combination supports massive data volumes, append-only workloads, and columnar storage for high-performance analytical queries.
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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