DEA-C01 Data Operations and Support Practice Question
A data engineer is monitoring a Redshift cluster that is experiencing slow query performance. The cluster has 4 dc2.large nodes. The engineer notices that disk space usage is at 85% across all nodes. Which action would MOST likely improve query performance?
⚠ Common exam trap
The DEA-C01 exam often tests the misconception that VACUUM or table design optimizations can resolve capacity-related performance issues, when in fact the immediate root cause is disk pressure triggering S3 offloading, which only scale-out or resize can fix.
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
✓
Increase the number of nodes to 8.
At 85% disk usage on dc2.large nodes, the cluster is approaching the threshold where Redshift begins to automatically offload data to Amazon S3, causing significant performance degradation due to increased I/O and network latency. Adding more nodes (option C) increases both compute capacity and total disk space, reducing per-node disk pressure and allowing the cluster to keep more data local for faster query execution.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Change the table design to use DISTKEY and SORTKEY.
Why it's wrong here
Table design changes require table recreation and do not immediately reduce disk usage.
- ✗
Enable compression on all columns.
Why it's wrong here
Compression is typically set at table creation; existing tables may already be compressed.
- ✓
Increase the number of nodes to 8.
Why this is correct
Adding nodes increases disk capacity and I/O throughput, reducing disk pressure and improving query performance.
- ✗
Run the VACUUM command to reclaim space.
Why it's wrong here
VACUUM cleans up deleted rows but does not reduce overall data volume.
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.