MLS-C01 Data Engineering Practice Question
A research institution is building a data lake to store genomics data. Each experiment generates multiple files totaling about 500 GB. The data is stored in Amazon S3 and needs to be processed by multiple machine learning (ML) training jobs running on Amazon SageMaker. The data has a high churn rate; after 30 days, most data becomes irrelevant and should be moved to Amazon S3 Glacier Deep Archive. The institution wants to minimize storage costs while maintaining data durability. Which S3 storage class should they use for the first 30 days?
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 S3 Intelligent-Tiering for all data, and set a lifecycle policy to transition to S3 Glacier Deep Archive after 30 days.
S3 Intelligent-Tiering is the most cost-effective storage class for the first 30 days because it automatically moves data between frequent and infrequent access tiers based on usage, without any retrieval fees. This is ideal for genomics data that may have unknown or changing access patterns during the initial processing period. After 30 days, a lifecycle rule transitions the data to S3 Glacier Deep Archive for long-term storage, minimizing costs. S3 Standard is more expensive for data that may not be accessed frequently, S3 One Zone-IA lacks durability across Availability Zones, and S3 Glacier Instant Retrieval is designed for long-lived, rarely accessed data and is not cost-effective for the first 30 days.
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 S3 Intelligent-Tiering for all data, and set a lifecycle policy to transition to S3 Glacier Deep Archive after 30 days.
Why this is correct
Intelligent-Tiering automatically optimizes costs by moving data to lower-cost tiers when not accessed, and it provides high durability.
- ✗
Use S3 One Zone-IA for all data, and set a lifecycle policy to transition to S3 Glacier Deep Archive after 30 days.
Why it's wrong here
S3 One Zone-IA does not provide the durability of multiple Availability Zones; data loss risk is higher.
- ✗
Use S3 Standard for all data, and set a lifecycle policy to transition to S3 Glacier Deep Archive after 30 days.
Why it's wrong here
S3 Standard is more expensive than necessary if data is accessed only for a short period.
- ✗
Use S3 Glacier Instant Retrieval for all data, and set a lifecycle policy to transition to S3 Glacier Deep Archive after 30 days.
Why it's wrong here
Glacier Instant Retrieval is designed for rarely accessed data that requires millisecond retrieval; it is more expensive than Standard for data that is accessed frequently.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
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