AZ-305 Design data storage solutions Practice Question
A company stores petabytes of image files for a content delivery network. The images are accessed frequently for the first week, then rarely afterward. They must be retained for 5 years for compliance. The company wants to minimize storage costs while maintaining performance for frequently accessed data. Which storage solution and tier strategy should they recommend?
⚠ Common exam trap
Watch out — candidates often choose the Archive tier for long-term retention without considering the performance impact of frequent access during the first week, overlooking that Archive requires hours to rehydrate and incurs high read costs, making it unsuitable for the initial high-access period.
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
✓
Azure Blob Storage with a lifecycle policy: Hot for 7 days, Cool for the remainder of 5 years
Azure Blob Storage with a lifecycle policy is the correct solution because it automatically transitions blobs from the Hot tier (for frequent access during the first week) to the Cool tier (for rare access over the remaining 5 years), minimizing storage costs while maintaining low-latency performance for the initial high-access period. The Hot tier provides high throughput and low access costs for frequently read data, while the Cool tier offers lower storage costs for infrequently accessed data, meeting both performance and compliance retention requirements.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Azure Blob Storage with a lifecycle policy: Hot for 7 days, Cool for the remainder of 5 years
Why this is correct
This is correct because Azure Blob Storage is optimized for serving large volumes of static objects over HTTP/S to Azure CDN or Front Door, and its lifecycle management feature automates movement between access tiers based on blob age. Setting a rule for Hot for 7 days matches the period of heavy read traffic, after which transitioning to Cool for the remaining 5 years dramatically reduces storage cost while still providing sub-second latency for occasional access. The lifecycle policy evaluates each blob's last modification date and enforces the tier change without manual intervention, exactly fitting a cost-sensitive archive-with-fast-recent-access pattern.
- ✗
Azure Files with premium tier
Why it's wrong here
Azure Files Premium tier uses SSD-backed shares designed for low-latency SMB access, not for serving petabytes of static image objects via HTTP to a content delivery network; it lacks native CDN integration and object-level tiering to cold storage. This option tempts because Premium tier offers high IOPS for frequently accessed files, which suits a shared file system for active workloads, but the scenario demands blob-based storage with lifecycle management to archive rarely accessed data after one week.
- ✗
Azure Data Lake Storage Gen2 with hot tier only
Why it's wrong here
Azure Data Lake Storage Gen2 provides a hierarchical namespace on top of Blob Storage, but selecting it with a hot-tier-only configuration is wrong for this scenario because it abandons the lifecycle management benefit that the question demands. While ADLS Gen2 does support tiering policies, the specified option locks all petabyte-scale image data in the hot tier for 5 years, incurring roughly 3–5x the storage cost of Cool tier with zero access after the first week. Moreover, the hierarchical namespace is not needed for CDN origin serving of immutable images and would only add operational complexity without improving HTTP delivery performance.
- ✗
Azure Blob Storage with archive tier from day 1
Why it's wrong here
Setting the default access tier to Archive from day 1 is wrong because Archive tier is designed for rarely accessed data with retrieval times measured in hours and a per-GB retrieval charge that makes frequent reads extremely costly. In the first 7 days, the images will be actively fetched by the CDN or end users, so placing them directly in Archive would force expensive and slow rehydration operations for every cache miss. A lifecycle policy should instead start the blobs in Hot to handle the high initial demand and only move them to Cool (or later Archive) after the access pattern drops, which is why this option fails the cost and performance requirements.
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 |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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