DP-900 Describe core data concepts Practice Question
A company stores customer transaction data in Azure Blob Storage. The data is rarely accessed after 30 days, but must be retained for 7 years for compliance. Which access tier minimizes storage cost while meeting the retention requirement?
⚠ Common exam trap
Candidates often choose the Cool tier thinking it balances cost and access, but they overlook that the Archive tier is significantly cheaper for data that is accessed less than once a year, which is typical for 7-year compliance retention.
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
✓
Archive tier
The Archive tier is the correct choice because it offers the lowest storage cost for data that is rarely accessed, which aligns with the scenario where data is accessed infrequently after 30 days but must be retained for 7 years. Azure Blob Storage's Archive tier is designed for long-term retention with a retrieval latency of several hours, making it cost-effective for compliance-driven data that does not require immediate access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Hot tier
Why it's wrong here
Hot tier is optimized for data accessed or modified frequently, delivering millisecond latency; however, its per-GB storage price is substantially higher than Cool or Archive. For customer transaction data that is rarely accessed after ingestion and must be retained for years, paying Hot-tier storage rates would be wasteful. This is why it is incorrect for this scenario.
- ✗
Cool tier
Why it's wrong here
Cool tier is designed for data accessed only a few times per month, with a lower storage cost than Hot but a higher cost than Archive. It also enforces a 30-day minimum storage duration and applies early-deletion penalties, making it inefficient for a long-term archive that needs no recurring access. Thus it is more expensive and less suitable than Archive for this use case.
- ✗
Premium tier
Why it's wrong here
Premium tier is built for high-throughput, low-latency workloads using SSD-backed block blobs and is priced at the highest rate of all tiers. Using it for long-term retention of rarely accessed transaction data is economically irrational and fails to meet the requirement of cost optimization. Therefore it is not the correct choice.
- ✓
Archive tier
Why this is correct
Archive tier offers the lowest storage cost of any Blob Storage tier, ideal for data that is seldom accessed and due for long-term retention. It accepts retrieval latency of up to 15 hours and carries a minimum 180-day storage commitment, making it perfect for dormant customer transaction records that must be preserved for compliance. This is why it is the correct selection.
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
Data
Data is raw, unprocessed information, like numbers, words, or measurements, that can be stored, processed, and analyzed by computers.
Key term
Blob storage
Blob storage is a cloud service for storing large amounts of unstructured data, such as text or binary data, like documents, images, and videos.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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