The answer is to use Azure Key Vault Managed HSM with customer-managed keys and enable double encryption with infrastructure encryption. This solution is correct because Managed HSM provides FIPS 140-2 Level 3 validated hardware security modules that isolate your key material from Microsoft administrators, who have no export or visibility permissions, while infrastructure encryption adds a second layer of platform-managed encryption for true double encryption. On the AZ-305 exam, this scenario tests your understanding of the encryption hierarchy and the distinction between standard Key Vault and Managed HSM, with a common trap being to choose standard Key Vault—which does not guarantee Microsoft administrator isolation. Remember that Managed HSM is the only option that meets the “no Microsoft access” requirement for customer-managed keys, and the phrase “double encryption” signals the need for infrastructure encryption. A useful memory tip: “Managed HSM locks the key, infrastructure locks the disk twice.”
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 stores sensitive customer data in Azure Blob Storage. You must ensure that data is encrypted at rest using customer-managed keys (CMK) and that key rotation is automated. You also need to prevent data from being accessed by any Microsoft administrator. Which solution should you implement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use Azure Key Vault Managed HSM with customer-managed keys and enable double encryption with infrastructure encryption.
Option C is correct because Azure Key Vault Managed HSM provides FIPS 140-2 Level 3 validated hardware security modules (HSMs) for storing customer-managed keys (CMK), supports automated key rotation, and enables double encryption via infrastructure encryption. This ensures that data is encrypted at rest with a customer-controlled key, and the use of Managed HSM prevents Microsoft administrators from accessing the key material, as the HSM is isolated and Microsoft has no export or visibility permissions.
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.
✗
Use Azure Key Vault (Standard) to store customer-managed keys and enable automatic key rotation.
Why it's wrong here
Standard Key Vault does not guarantee tenant isolation; Microsoft administrators may still have access.
✗
Use Azure Disk Encryption with customer-managed keys stored in Azure Key Vault.
Why it's wrong here
Disk Encryption applies to VMs, not Blob Storage.
✓
Use Azure Key Vault Managed HSM with customer-managed keys and enable double encryption with infrastructure encryption.
Why this is correct
Managed HSM provides tenant-controlled keys and isolation; double encryption adds an additional layer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable Azure Storage Service Encryption with platform-managed keys.
Why it's wrong here
Platform-managed keys are managed by Microsoft, not customer-controlled.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Azure Key Vault (Standard) with Managed HSM, assuming both provide the same level of isolation and security, but only Managed HSM offers FIPS 140-2 Level 3 HSM-backed keys and prevents Microsoft administrator access, which is critical for sensitive customer data scenarios.
Detailed technical explanation
How to think about this question
Azure Key Vault Managed HSM uses a dedicated, single-tenant HSM cluster that is FIPS 140-2 Level 3 validated, ensuring that cryptographic keys are isolated from Microsoft operations. Double encryption with infrastructure encryption adds a second layer of encryption at the storage infrastructure level using a platform-managed key, while the customer-managed key encrypts the data encryption key (DEK) via envelope encryption. This combination ensures that even if one layer is compromised, the data remains protected, and Microsoft administrators cannot access the customer-managed key stored in the Managed HSM.
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: Use Azure Key Vault Managed HSM with customer-managed keys and enable double encryption with infrastructure encryption. — Option C is correct because Azure Key Vault Managed HSM provides FIPS 140-2 Level 3 validated hardware security modules (HSMs) for storing customer-managed keys (CMK), supports automated key rotation, and enables double encryption via infrastructure encryption. This ensures that data is encrypted at rest with a customer-controlled key, and the use of Managed HSM prevents Microsoft administrators from accessing the key material, as the HSM is isolated and Microsoft has no export or visibility permissions.
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. A company needs to store sensitive customer data in Azure Blob Storage with encryption at rest using customer-managed keys (CMK) stored in a hardware security module (HSM). Which Azure service should they use to manage the keys?
hard
A.Azure Key Vault (Premium tier)
B.Azure Information Protection
C.Azure Key Vault (Standard tier)
✓ D.Azure Key Vault Managed HSM
Why D: Azure Key Vault Managed HSM is a fully managed, highly available, single-tenant HSM that is FIPS 140-2 Level 3 validated. It allows you to store customer-managed encryption keys (CMKs) in a hardware security module (HSM) for Azure Storage encryption at rest, meeting the requirement for HSM-backed key storage. The Premium tier of Azure Key Vault also supports HSM-backed keys, but the question specifies 'stored in a hardware security module (HSM)', and Managed HSM provides dedicated HSM partitions with stronger isolation and compliance.
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Question Discussion
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