Azure Data Lake Storage Gen2 is the correct choice because it uniquely combines a hierarchical namespace with POSIX-like ACLs, enabling fine-grained access control at the file and directory level while supporting petabyte-scale analytical workloads. This service is built on Azure Blob Storage but adds a true directory structure, allowing big data engines like Azure Synapse, Spark, and Hadoop to process data in parallel with high throughput. On the Microsoft Azure Solutions Architect Expert AZ-305 exam, this question tests your ability to differentiate storage services for data lake scenarios—common traps include choosing standard Blob Storage (which lacks hierarchical namespaces) or Azure Files (which is designed for SMB sharing, not petabyte-scale analytics). Remember that ADLS Gen2 is the only Azure storage service that delivers both a hierarchical namespace and fine-grained ACLs at scale. A helpful memory tip: think “Gen2 for genealogy”—it organizes data like a family tree, with permissions inherited from parent directories down to individual files.
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 data platform must support analytical queries over petabytes of files in a data lake, while preserving hierarchical namespaces and fine-grained ACLs. Which storage service should you design around?
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.
Azure Data Lake Storage Gen2 (ADLS Gen2) is the correct choice because it combines a hierarchical namespace with POSIX-like ACLs, enabling fine-grained access control at the file and directory level while supporting petabyte-scale analytical workloads. It is built on Azure Blob Storage, providing high-throughput and parallel processing for big data analytics engines like Azure Synapse, Spark, and Hadoop.
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 Data Lake Storage Gen2.
Why this is correct
It provides hierarchical namespace and data lake semantics for analytics workloads.
Related concept
Read the scenario before looking for a memorised answer.
✗
Azure Files premium shares.
Why it's wrong here
Azure Files is SMB/NFS file sharing, not the best design for petabyte-scale analytical data lakes.
✗
Azure Table Storage.
Why it's wrong here
Table Storage is a NoSQL key-value store, not a file-based analytical lake.
✗
Azure Queue Storage.
Why it's wrong here
Queue Storage is for messaging, not analytical storage.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse Azure Files (which also supports ACLs) with ADLS Gen2, overlooking that Azure Files is optimized for shared file access (SMB/NFS) and not for petabyte-scale analytical data lake workloads with hierarchical namespace and POSIX ACLs.
Detailed technical explanation
How to think about this question
ADLS Gen2 implements a hierarchical namespace by extending Blob Storage with a file system abstraction, allowing operations like atomic directory renames and POSIX-compliant ACLs (owner, owning group, and named users/groups). Under the hood, it uses a two-level index (directory and file) to support efficient path-based access, which is critical for tools like Apache Spark that rely on directory listing and file-level security. In real-world scenarios, this enables fine-grained data governance, such as granting read-only access to specific subdirectories for different teams while maintaining full control for administrators.
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. — Azure Data Lake Storage Gen2 (ADLS Gen2) is the correct choice because it combines a hierarchical namespace with POSIX-like ACLs, enabling fine-grained access control at the file and directory level while supporting petabyte-scale analytical workloads. It is built on Azure Blob Storage, providing high-throughput and parallel processing for big data analytics engines like Azure Synapse, Spark, and Hadoop.
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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. You are designing a data lake for advanced analytics in Azure. The data includes structured, semi-structured, and unstructured data. The solution must support schema-on-read and have the ability to query using SQL. Which Azure service should you choose?
hard
A.Azure Blob Storage.
B.Azure SQL Database.
✓ C.Azure Data Lake Storage Gen2.
D.Azure Cosmos DB.
Why C: Option D is correct because Azure Data Lake Storage Gen2 provides a hierarchical namespace for storing all data types and integrates with query engines like Azure Synapse SQL for schema-on-read. Option A is wrong because Azure SQL Database is for structured data only. Option B is wrong because Azure Cosmos DB is for transactional workloads, not data lake. Option C is wrong because Azure Blob Storage lacks the hierarchical namespace needed for a data lake.
Last reviewed: Jun 11, 2026
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