The answer is Azure Blob Storage with immutability policies (WORM). This service is optimized for write once read many transactional records because it enforces a legal hold or time-based retention policy that prevents any modification or deletion after data is written, ensuring the immutable state required for compliance. On the AZ-900 exam, this scenario tests your understanding of which Azure service meets strict regulatory requirements for financial transactions or audit logs, where data integrity is paramount. A common trap is confusing this with Azure Cosmos DB, which supports multiple write patterns, or Azure Files, which allows edits. Remember the memory tip: “WORM” stands for Write Once, Read Many, and Blob Storage is the only service that locks data in place like a digital vault.
AZ-900 Describe Azure architecture and services Practice Question
This AZ-900 practice question tests your understanding of describe azure architecture and services. 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.
Which Azure storage service is optimized for storing transactional records where data is written once and read many times?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Azure Blob Storage with immutability policies (WORM)
Azure Blob Storage with immutability policies (WORM) is optimized for storing transactional records that are written once and read many times because it enforces a write-once-read-many (WORM) state, preventing data from being modified or deleted after it is written. This makes it ideal for compliance scenarios like financial transactions or audit logs where data integrity and immutability are critical.
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 Queue Storage
Why it's wrong here
Queue Storage is for inter-application messaging, not immutable transactional record storage.
✓
Azure Blob Storage with immutability policies (WORM)
Why this is correct
Blob Storage with WORM policies allows writing data once and prevents modification or deletion for compliance.
Related concept
Read the scenario before looking for a memorised answer.
✗
Azure Files
Why it's wrong here
Azure Files provides SMB file shares; it's not specifically optimized for WORM transactional records.
✗
Azure Data Lake Storage
Why it's wrong here
Data Lake is for analytics workloads; WORM-protected Blob Storage is for immutable transactional records.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Azure Blob Storage with immutability policies (WORM) with Azure Data Lake Storage, assuming both are optimized for analytics, but Data Lake Storage lacks native WORM immutability and is designed for high-throughput data processing, not transactional record retention.
Detailed technical explanation
How to think about this question
Azure Blob Storage immutability policies use a time-based retention policy or a legal hold to enforce WORM behavior at the container or blob level. Under the hood, the Azure Storage service tracks a retention interval in the blob metadata and rejects any PUT or DELETE operations that would violate the policy, even from the storage account owner. In a real-world scenario, a financial institution might use this to store transaction logs for regulatory compliance (e.g., SEC Rule 17a-4), ensuring records cannot be tampered with for a specified period.
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-900 question in full detail.
Describe Azure architecture and services — This question tests Describe Azure architecture and services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Azure Blob Storage with immutability policies (WORM) — Azure Blob Storage with immutability policies (WORM) is optimized for storing transactional records that are written once and read many times because it enforces a write-once-read-many (WORM) state, preventing data from being modified or deleted after it is written. This makes it ideal for compliance scenarios like financial transactions or audit logs where data integrity and immutability are critical.
What should I do if I get this AZ-900 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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