AZ-305 Design data storage solutions Practice Question
Your company is designing a data lake solution for IoT telemetry data. The data is ingested continuously and must be stored cost-effectively while allowing occasional interactive queries. The data has a lifespan of 90 days for hot access and 3 years for archived access. Which Azure storage tiering strategy minimizes costs?
⚠ Common exam trap
Watch out — candidates often assume Cool tier is sufficient for all data to save costs, but they overlook the need for hot access during the first 90 days and the even lower Archive tier for long-term retention, leading to higher overall costs.
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
✓
Use Azure Blob Storage with lifecycle management: Hot for 90 days, then Cool, then Archive after 3 years
Azure Blob Storage lifecycle management can automatically transition data from Hot to Cool to Archive tiers based on age, minimizing costs for IoT telemetry that needs 90 days of hot access and 3 years of archival. The Hot tier provides low-latency access for interactive queries, Cool offers lower storage cost for infrequent access, and Archive provides the lowest cost for long-term retention. This tiering strategy aligns with the data's lifespan and access patterns, reducing overall storage expenses compared to keeping all data in a single tier.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use Azure Blob Storage with only Hot tier for 90 days, then delete
Why it's wrong here
Deleting blobs after 90 days directly violates the stated 3-year retention requirement, as historical IoT telemetry must remain available for compliance and long-term trend analysis. While the Hot tier appropriately handles the high-frequency access during the initial phase, the subsequent deletion irreversibly loses data and cannot be remediated, making this option fundamentally unsuitable regardless of cost savings.
- ✓
Use Azure Blob Storage with lifecycle management: Hot for 90 days, then Cool, then Archive after 3 years
Why this is correct
This approach uses Azure Blob Storage lifecycle management policies to automatically transition blobs from Hot to Cool after 90 days of frequent access, then to Archive after 3 years, aligning with the retention period. The Archive tier offers the lowest storage cost for rarely accessed historical data while preserving it for future analytics, and the automated transitions reduce operational overhead and optimize cost without compromising data availability.
- ✗
Use Azure Blob Storage with Cool tier for all data
Why it's wrong here
While Cool tier has lower storage costs than Hot, it is designed for data infrequently accessed and incurs higher per-access charges and an early deletion penalty (30-day minimum). For the first 90 days, IoT telemetry is actively queried and analyzed, making Cool tier costlier and less performant than Hot tier for that phase; additionally, using Cool for all data fails to leverage Archive's greater savings for the 3-year archival requirement.
- ✗
Use Azure Files with lifecycle management to Archive after 90 days
Why it's wrong here
Azure Files is a managed file share service using SMB/NFS protocols, not an object storage solution, and it lacks native data lake integrations like hierarchical namespaces or the full analytics ecosystem available with Azure Data Lake Storage Gen2. Furthermore, its archive tier is limited and not equivalent to Blob Archive, and archiving after 90 days fails to maintain a hot/cool tiering strategy for the full 3-year lifespan, making this option unsuitable.
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
This AZ-305 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-305 exam.