DEA-C01 Data Store Management Practice Question
A company uses Amazon EMR to run Spark jobs on a cluster of 20 nodes. The cluster stores intermediate data on Amazon S3 using EMRFS. The company's data engineering team notices that the Spark jobs are running slower than expected. Upon investigating, they find that the cluster is experiencing high network I/O and that the S3 storage costs have increased significantly. The team suspects that the Spark jobs are writing too much intermediate data to S3. The jobs are performing many shuffle operations. The team wants to optimize the job performance and reduce costs without modifying the Spark application code. What should the data engineer do?
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
✓
Configure the EMR cluster to use instance store volumes for intermediate data instead of EMRFS.
Configuring the EMR cluster to use instance store volumes for intermediate data instead of EMRFS reduces the amount of data written to Amazon S3 during shuffle operations. Instance store volumes provide local, ephemeral storage that is faster and avoids network I/O and S3 costs associated with EMRFS. This directly addresses the high network I/O and increased S3 storage costs without modifying the Spark application code. Option A is incorrect because enabling S3 server-side encryption does not affect performance or reduce the volume of data written; it only encrypts data at rest. Option B is incorrect because increasing the size of EBS root volumes does not change how shuffle data is stored; EMR uses instance store or EMRFS for shuffle, not EBS root volumes. Option D is incorrect because adding more nodes may increase network I/O and cost, and does not prevent the job from writing intermediate data to S3.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable S3 server-side encryption on the S3 bucket to reduce storage costs.
Why it's wrong here
Encryption does not reduce storage costs.
- ✗
Increase the size of the EBS root volumes on the cluster nodes to store more intermediate data locally.
Why it's wrong here
EBS volumes are not used for shuffle by default; increasing them won't help.
- ✓
Configure the EMR cluster to use instance store volumes for intermediate data instead of EMRFS.
Why this is correct
Instance store provides local ephemeral storage, reducing S3 dependency and network I/O.
- ✗
Add more nodes to the cluster to distribute the shuffle load.
Why it's wrong here
More nodes may increase network I/O and cost.
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 |
Go deeper
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DEA-C01 practice question is part of Courseiva's free Amazon Web Services 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 DEA-C01 exam.