AZ-900 Describe Azure architecture and services Practice Question
A company uses Azure Blob Storage to store compliance documents that are required to be kept for 10 years. The documents are very rarely accessed; on average, only 2-3 requests per year are made, usually for audits. The company needs the lowest possible storage cost. When a document is requested, the company can tolerate a retrieval time of up to 15 hours. Which Azure Blob Storage access tier should the company use?
⚠ Common exam trap
A common mix-up: candidates confuse 'lowest storage cost' with 'lowest overall cost' and overlook the retrieval latency and rehydration costs of the Archive tier, or mistakenly choose Cool tier thinking it balances cost and access speed without recognizing that Archive is significantly cheaper for such rare access patterns.
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 access tier
The Archive access tier is designed for data that is rarely accessed and has a flexible retrieval time, offering the lowest storage cost among Azure Blob Storage tiers. With only 2-3 requests per year and a tolerance for up to 15-hour retrieval latency, the Archive tier (which typically takes up to 15 hours to rehydrate) perfectly matches the requirements while minimizing storage expenses.
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 access tier
Why it's wrong here
The Hot tier is designed for frequent read/write access and carries the highest per-gigabyte storage cost among the standard access tiers (Hot, Cool, Cold, Archive). Selecting Hot for compliance documents that are rarely accessed would maximize storage spend without any benefit, because fast retrieval is unnecessary. It should only be used when data is actively and continuously accessed, not for dormant, low-cost archival storage.
When this WOULD be correct
A company needs to store data that is accessed frequently (multiple times per day) and requires low latency (milliseconds) for retrieval. The priority is on access performance rather than storage cost.
- ✗
Cool access tier
Why it's wrong here
The Cool tier is for data that is infrequently accessed (about once per month or less) and has lower storage cost than Hot, but higher than Archive. It offers immediate retrieval, which is not necessary here, and would still be more expensive than Archive for this use case.
When this WOULD be correct
A company stores backup data that is accessed a few times per month and requires retrieval within seconds. They need lower storage cost than Hot but cannot tolerate hours of latency. The Cool tier would be the best choice.
- ✓
Archive access tier
Why this is correct
The Archive tier is the lowest-cost storage tier, designed for data that is rarely accessed and can tolerate retrieval latencies of up to 15 hours. This matches the company's requirement for low cost and acceptable retrieval time, making it the correct choice.
- ✗
Premium access tier
Why it's wrong here
The Premium tier is a high-performance block-blob offering built on SSD, intended for latency-sensitive and high-transaction-rate workloads such as real-time analytics or interactive applications. Its storage cost is even higher than Hot and is completely at odds with a 'lowest-cost' goal for rarely accessed documents. Unlike standard tiers, Premium also lacks automatic lifecycle tiering to Archive, making it an especially poor fit for compliance archives.
When this WOULD be correct
A company needs to store frequently accessed data (e.g., for real-time analytics) with sub-millisecond latency and high transaction rates, and cost is not the primary concern.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-900 exam frequently reuses these exact scenarios with slightly different constraints.
✓Archive access tierCorrect answer▾
Why this is correct
The Archive tier is the lowest-cost storage tier, designed for data that is rarely accessed and can tolerate retrieval latencies of up to 15 hours. This matches the company's requirement for low cost and acceptable retrieval time, making it the correct choice.
✗Hot access tierWrong answer — click to see why▾
Why this is wrong here
The Hot access tier is optimized for frequent access and has the highest storage cost, which contradicts the requirement for lowest possible storage cost for rarely accessed documents.
★ When this WOULD be the correct answer
A company needs to store data that is accessed frequently (multiple times per day) and requires low latency (milliseconds) for retrieval. The priority is on access performance rather than storage cost.
Why candidates choose this
Candidates may assume 'Hot' is always the best default tier, or they may not fully understand that the question emphasizes lowest storage cost over access speed.
✗Cool access tierWrong answer — click to see why▾
Why this is wrong here
The Cool access tier has higher storage costs than Archive and is optimized for data accessed infrequently but with immediate retrieval needs (seconds), not for data with a 15-hour retrieval tolerance and only 2-3 requests per year.
★ When this WOULD be the correct answer
A company stores backup data that is accessed a few times per month and requires retrieval within seconds. They need lower storage cost than Hot but cannot tolerate hours of latency. The Cool tier would be the best choice.
Why candidates choose this
Candidates may think 'Cool' is the lowest-cost tier for infrequently accessed data, overlooking that Archive is even cheaper and suitable for data with very low access frequency and high retrieval latency tolerance.
✗Premium access tierWrong answer — click to see why▾
Why this is wrong here
The Premium access tier is designed for low-latency, high-throughput workloads and has the highest storage cost, which contradicts the requirement for the lowest possible storage cost and tolerance for up to 15-hour retrieval times.
★ When this WOULD be the correct answer
A company needs to store frequently accessed data (e.g., for real-time analytics) with sub-millisecond latency and high transaction rates, and cost is not the primary concern.
Why candidates choose this
Candidates may mistakenly think 'Premium' implies better overall performance or cost-efficiency, or they may confuse it with the Archive tier's retrieval cost structure.
Analysis generated from the official AZ-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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
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.
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-900 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-900 exam.