MLS-C01 Data Engineering Practice Question
A research lab stores large genomic datasets in Amazon S3 Glacier Deep Archive. They need to run a one-time analysis on a subset of 10 PB of data. The analysis will use an Amazon EMR cluster with Amazon S3 as the data source. What is the MOST cost-effective and performant way to make the data available for the EMR cluster?
⚠ Common exam trap
A common mix-up: candidates assume Expedited retrieval is always the fastest and thus best for performance, ignoring the massive cost difference at petabyte scale and the fact that Bulk retrieval's 48-hour window is acceptable for a one-time analysis.
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
✓
Initiate a Bulk retrieval request and restore the data to S3 Standard for the duration of the analysis
Bulk retrieval is the most cost-effective retrieval tier for large, non-urgent data from S3 Glacier Deep Archive, completing within 48 hours. Restoring to S3 Standard provides direct, high-throughput access for the EMR cluster, and deleting the data after analysis avoids ongoing storage costs. This approach balances performance (EMR reads from S3 Standard) with minimal cost (Bulk retrieval is the cheapest retrieval option).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Restore the data to S3 Standard-IA and delete after the analysis
Why it's wrong here
Standard-IA has a minimum storage charge and retrieval cost that may be higher than Standard for single access.
- ✗
Configure the EMR cluster to read directly from Glacier Deep Archive using S3 Console
Why it's wrong here
EMR cannot read directly from Glacier Deep Archive; data must be restored first.
- ✓
Initiate a Bulk retrieval request and restore the data to S3 Standard for the duration of the analysis
Why this is correct
Bulk retrieval is the lowest cost tier, and restoring to Standard avoids IA minimum charges.
- ✗
Initiate an Expedited retrieval request and use the temporary copy for the EMR cluster
Why it's wrong here
Expedited is more expensive than Bulk and not necessary for a batch job.
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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