DP-900 Describe an analytics workload on Azure Practice Question
A data engineer needs to design a solution for a healthcare organization that must store patient records for 7 years to comply with regulatory requirements. The data will be accessed infrequently after the first year. Which Azure storage tier should be used for data older than one year?
⚠ Common exam trap
Microsoft often tests the misconception that Archive tier is the cheapest and therefore always the best for old data, but the trap here is ignoring the retrieval latency and access requirements—Archive is only appropriate if data can tolerate hours of delay for rehydration.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Cool tier
The Cool tier is designed for data that is accessed infrequently but must be available immediately when needed, with a minimum storage duration of 30 days. Since patient records older than one year are accessed rarely but may still require low-latency retrieval for compliance audits, Cool tier balances cost and accessibility. Hot tier is for frequent access, Archive tier has a retrieval latency of hours (not suitable for occasional access), and Transaction-optimized is not a standard Azure Blob Storage tier.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Transaction-optimized tier
Why it's wrong here
Transaction-optimized tier is an Azure Files service tier, not an Azure Blob Storage access tier. It is engineered for high-throughput, low-latency file workloads with heavy IOPS requirements, not for archival or compliance retention. For a healthcare solution retaining records for seven years, this tier would be both inapplicable and cost-prohibitive, because it prioritizes performance over storage economy.
- ✓
Cool tier
Why this is correct
Cool tier is the correct choice for healthcare data older than one year because it provides low storage costs while keeping data immediately readable without rehydration. It is designed for data that is infrequently accessed but needs to be held for at least 30 days, which aligns with a seven-year retention requirement. Although access fees are higher than Hot, the overall cost for rarely read data is significantly lower, and there is no 180-day minimum or retrieval latency as in Archive.
- ✗
Archive tier
Why it's wrong here
Archive tier has the lowest storage cost but forces data to be rehydrated before any read, introducing latency of up to several hours and paying a premium for retrieval. It also carries a 180-day minimum storage duration, so early deletion would incur an additional charge, which is excessive for a scenario where older healthcare records might still need occasional audit or treatment access. For a seven-year retention policy, the Cool tier avoids these operational penalties while still being cost-effective.
- ✗
Hot tier
Why it's wrong here
Hot tier is engineered for high-frequency access, so it carries the highest storage cost among Blob Storage tiers and would be financially wasteful for data read only rarely. In a healthcare context, data older than one year is unlikely to be accessed daily, so paying a premium for storage while underutilizing that speed violates cost-optimization principles. Use Hot only for active datasets; infrequent access patterns make Cool tier the better fit.
Quick reference
Azure Blob Storage Tier Comparison
| Tier | Storage Cost | Retrieval Cost | Latency | Use Case |
|---|---|---|---|---|
| Hot | Highest | Lowest | Immediate | Active data, frequent reads |
| Cool | Lower | Higher | Immediate | Data accessed < once / month |
| Cold | Lower still | Higher | Immediate | Data accessed < once / quarter |
| Archive | Lowest | Highest + rehydration delay | Hours | Long-term compliance retention |
Go deeper
Related to this question
Learn chapter
Data Roles and Core Concepts
Key term
Azure Storage
Azure Storage is Microsoft's cloud-based service for storing data like files, messages, and backups with high durability and scalability.
Key term
Data
Data is raw, unprocessed information, like numbers, words, or measurements, that can be stored, processed, and analyzed by computers.
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