AZ-900 Describe Azure architecture and services Practice Question
Which Azure storage tier should be used for data that is rarely accessed, can tolerate several hours of retrieval latency, and needs to be stored at the lowest cost?
⚠ Common exam trap
It's easy for candidates to confuse 'rarely accessed' with 'infrequently accessed' and choose Cool tier, forgetting that the Archive tier is the only one that tolerates hours of retrieval latency and offers the absolute lowest cost for truly dormant data.
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 designed for data that is rarely accessed and can tolerate several hours of retrieval latency, offering the lowest storage cost among Azure Blob Storage tiers. It requires rehydration to a Hot or Cool tier before reading, which typically takes up to 15 hours, making it ideal for long-term backup, archival, and compliance data.
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 frequently accessed, active data, providing low latency and fast throughput but charging a higher storage price per GB than Cool or Archive. Because the scenario calls for rarely accessed archival data, retaining it in Hot tier would waste budget on ongoing storage costs and offer no performance benefit. Therefore, Hot tier is a poor fit based on both cost efficiency and the access pattern of the data.
- ✗
Cool tier
Why it's wrong here
Cool tier is designed for data that is infrequently accessed and stored for at least 30 days. While its storage price is lower than the Hot tier, it incurs higher per-GB access charges and early-deletion fees, and it does not offer the lowest storage cost. For purely archival data that is rarely read, the Archive tier is cheaper, making Cool an unnecessarily expensive middle ground.
- ✓
Archive tier
Why this is correct
Archive tier is the cheapest storage option in Azure Blob Storage for rarely accessed data, and it is the correct choice for this scenario. Data in the Archive tier must be rehydrated to Hot or Cool (or copied to another tier) before it can be read, a process that can take up to 15 hours. Since the data is archival and cost is the primary concern, Archive tier provides the lowest cost per GB, despite the rehydration delay.
- ✗
Premium tier
Why it's wrong here
Premium tier uses high-performance SSD-backed storage and is intended for latency-sensitive, frequently accessed data such as transactional workloads with high IOPS. It carries the highest per-GB cost of all Azure Blob Storage access tiers and provides no benefit for infrequently accessed archival data. Therefore, using Premium tier would dramatically inflate storage costs with no matching performance requirement.
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
Azure Regions and Geographies
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
Blob
A blob is a large piece of unstructured data, like a photo or video, stored in the cloud with a unique identifier.
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