Quick Answer
The answer is Azure Blob Storage with immutable storage, specifically a WORM (Write Once, Read Many) policy configured for a 99-year retention period. This solution is correct because it enforces data immutability, meaning backup data cannot be modified or deleted during the retention window, which directly satisfies long-term compliance requirements for regulatory audits. Additionally, Azure Storage Service Encryption secures data at rest, while HTTPS ensures encryption in transit, covering both security mandates. On the AZ-305 exam, this scenario tests your understanding of data protection and compliance solutions, often appearing as a trap where candidates mistakenly choose Azure Backup or Archive Storage—both lack the 99-year immutable lock capability. Remember that Azure Blob immutable storage supports a maximum retention of 99 years, not indefinite, and the policy must be set to "legal hold" or "time-based retention" to prevent premature deletion. A useful memory tip: "WORM for WORM—Write Once, Read Many for Years of Regulatory Mandates."
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 backup data from Azure Virtual Machines with a retention policy of 99 years to meet compliance requirements. The backups must be encrypted at rest and in transit. Which Azure storage solution should they use?
Azure Files
Why wrong: Not designed for backup retention.
Azure NetApp Files
Why wrong: For enterprise file workloads.
Azure Disk Storage
Why wrong: For VM disks, not backups.
Azure Blob Storage with immutable storage
Supports long-term retention and encryption.
Answer choices
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 immutable storage
Azure Blob Storage with immutable storage (specifically, a WORM policy with a retention period of up to 99 years) is the correct choice because it meets the 99-year retention requirement and provides encryption at rest (via Azure Storage Service Encryption) and in transit (via HTTPS). Immutable storage prevents data from being deleted or modified during the retention period, which is essential for long-term compliance backups.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Azure Files
Why it's wrong here
Not designed for backup retention.
Azure NetApp Files
Why it's wrong here
For enterprise file workloads.
Azure Disk Storage
Why it's wrong here
For VM disks, not backups.
Azure Blob Storage with immutable storage
Why this is correct
Supports long-term retention and encryption.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often confuse Azure Backup's retention limits (max 10 years for VM backups) with the 99-year immutable retention capability of Blob Storage, leading them to incorrectly choose Azure Disk Storage or Azure Files.
Detailed technical explanation
Immutable storage in Azure Blob Storage uses a time-based retention policy that locks blobs in a WORM (Write Once, Read Many) state; the maximum retention period is 99 years, and the policy can be set at the container level. Under the hood, Azure Storage Service Encryption (SSE) uses 256-bit AES encryption for data at rest, and HTTPS/TLS 1.2+ ensures encryption in transit. A real-world scenario is a financial institution required to retain audit logs for 99 years under SEC Rule 17a-4, which mandates immutable storage to prevent tampering.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
What to study next
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FAQ
Design data storage solutions — This question tests Design data storage solutions — Read the scenario before looking for a memorised answer..
The correct answer is: Azure Blob Storage with immutable storage — Azure Blob Storage with immutable storage (specifically, a WORM policy with a retention period of up to 99 years) is the correct choice because it meets the 99-year retention requirement and provides encryption at rest (via Azure Storage Service Encryption) and in transit (via HTTPS). Immutable storage prevents data from being deleted or modified during the retention period, which is essential for long-term compliance backups.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This AZ-305 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-305 exam.
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