AZ-900 Describe Azure architecture and services Practice Question
A company needs to store backup data that must be retained for 7 years. They want to store the data as cheaply as possible, and access may be rare. Which Azure Storage access tier is most cost-effective?
⚠ Common exam trap
Watch out — candidates often confuse 'cheapest storage cost' with 'cheapest overall cost,' overlooking the high retrieval costs and rehydration latency of the Archive tier, or they mistakenly choose Cool tier because it sounds 'cool enough' for rare access without considering the 7-year retention requirement.
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 most cost-effective option for data that must be retained for 7 years with rare access. It offers the lowest storage cost among Azure Blob Storage access tiers, specifically designed for long-term retention where retrieval latency of up to 15 hours is acceptable. This aligns perfectly with the requirement to minimize cost while meeting the 7-year retention period.
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
The Hot tier is built for data that is accessed or modified frequently, charging the highest storage cost (other than Premium) in exchange for zero retrieval latency. For a 7-year backup archive, daily availability and rapid access are not needed, so paying the premium per-GB price for the entire retention period is economically irrational. The Hot tier also has higher transaction fees on read operations, which would further inflate costs even on the rare occasions the backups are accessed.
When this WOULD be correct
A company needs to store data that is accessed frequently (e.g., daily) and requires low-latency access, with cost optimization for high read/write operations.
- ✗
Cool tier
Why it's wrong here
The Cool tier is optimized for data that is infrequently accessed but still needs immediate availability, with costs higher than Archive but lower than Hot. While it could store backups for 7 years, the ongoing storage expense over such a long period would be substantially greater than Archive due to higher per-GB pricing. Additionally, Cool tier's default access latency is in milliseconds, which is unnecessary for backups that are seldom retrieved. Therefore, it satisfies retention but not the financial goal of cost minimization.
When this WOULD be correct
A company needs to store data that is accessed infrequently (e.g., a few times per year) but requires retrieval within seconds, and the data will be retained for at least 30 days. In this scenario, Cool tier balances cost and availability.
- ✓
Archive tier
Why this is correct
The Archive tier is designed specifically for long-term retention of data that is accessed rarely, offering the lowest per-gigabyte storage cost among Azure Blob Storage tiers. Because these backups must be kept for 7 years and are unlikely to be read regularly, the retrieval latency of up to several hours (via rehydration) is acceptable. This makes Archive the most cost-effective and correct choice for meeting the retention requirement while minimizing expenditure.
- ✗
Premium tier
Why it's wrong here
The Premium tier delivers high-performance, low-latency access by backing blobs with solid-state drives, making it ideal for active workloads, not archival storage. Its per-gigabyte cost is the highest among all tiers, so retaining 7-year-old backups there would incur prohibitive storage charges. Backup data does not require sub-millisecond response times or high I/O throughput, making Premium tier entirely mismatched to both the access pattern and cost objectives.
When this WOULD be correct
A question requiring the lowest latency for frequently accessed data, such as an application needing sub-millisecond response times for active transactions, would make Premium tier the correct choice.
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 tierCorrect answer▾
Why this is correct
The Archive tier is designed specifically for long-term retention of data that is accessed rarely, offering the lowest per-gigabyte storage cost among Azure Blob Storage tiers. Because these backups must be kept for 7 years and are unlikely to be read regularly, the retrieval latency of up to several hours (via rehydration) is acceptable. This makes Archive the most cost-effective and correct choice for meeting the retention requirement while minimizing expenditure.
✗Hot tierWrong answer — click to see why▾
Why this is wrong here
The Hot tier is designed for frequently accessed data and has higher storage costs, making it unsuitable for long-term, rarely accessed backup retention over 7 years.
★ When this WOULD be the correct answer
A company needs to store data that is accessed frequently (e.g., daily) and requires low-latency access, with cost optimization for high read/write operations.
Why candidates choose this
Candidates may assume 'Hot' is always the best default tier, overlooking that cost-effectiveness for rare access favors cheaper tiers like Archive.
✗Cool tierWrong answer — click to see why▾
Why this is wrong here
The Cool tier is designed for data with moderate access frequency and a minimum 30-day storage duration, but the question specifies rare access and a 7-year retention period, making the Archive tier cheaper due to its lower storage cost.
★ When this WOULD be the correct answer
A company needs to store data that is accessed infrequently (e.g., a few times per year) but requires retrieval within seconds, and the data will be retained for at least 30 days. In this scenario, Cool tier balances cost and availability.
Why candidates choose this
Candidates may confuse 'cool' with 'cold' and assume it's the cheapest option for rarely accessed data, overlooking that Archive tier is specifically designed for long-term, rare-access storage at even lower cost.
✗Premium tierWrong answer — click to see why▾
Why this is wrong here
The Premium tier is designed for low-latency, high-performance workloads and is the most expensive tier, making it unsuitable for cheap, rarely accessed backup data retained for 7 years.
★ When this WOULD be the correct answer
A question requiring the lowest latency for frequently accessed data, such as an application needing sub-millisecond response times for active transactions, would make Premium tier the correct choice.
Why candidates choose this
Candidates may mistakenly think 'Premium' implies better overall value or durability, not realizing it is the most costly tier and inappropriate for cold storage scenarios.
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
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.
About these practice questions
Courseiva writes every AZ-900 question from scratch — 981 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
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.