DEA-C01 Data Store Management Practice Question
A company uses Amazon Redshift for data warehousing. The data engineering team notices that queries are slow due to high disk I/O. The team wants to improve query performance without changing the cluster configuration. Which action should the team take?
⚠ Common exam trap
Candidates often confuse maintenance commands (ANALYZE, VACUUM) with design changes, or think scaling out (adding nodes) is allowed when the question explicitly forbids changing cluster configuration.
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
✓
Redesign tables with appropriate sort keys and distribution styles.
Redesigning tables with appropriate sort keys and distribution styles directly addresses high disk I/O by minimizing data scanning and reducing data movement across nodes. Sort keys enable Redshift to skip irrelevant blocks via zone maps, while distribution styles (KEY, ALL, EVEN) optimize data locality for joins and aggregations, reducing I/O without changing cluster configuration.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Increase the number of nodes in the cluster.
Why it's wrong here
Adding nodes changes the cluster configuration, which the stem explicitly excludes, and it redistributes data rather than reducing the I/O each query performs. It is tempting because more nodes raise throughput, but the requirement is a no-configuration-change action, which VACUUM satisfies.
- ✓
Redesign tables with appropriate sort keys and distribution styles.
Why this is correct
Sort keys reduce the blocks scanned by enabling zone-map pruning, while distribution styles co-locate joined rows on the same slice, cutting inter-node network traffic. Both target disk I/O and skew directly, satisfying the constraint of improving performance without altering cluster configuration.
- ✗
Run the ANALYZE command to update table statistics.
Why it's wrong here
ANALYZE refreshes planner statistics, improving plan choice, but it does not reduce the disk I/O caused by unsorted data and bloated blocks. It is tempting because stale statistics do cause poor plans, yet the stem attributes slowness to disk I/O, which VACUUM's sort and space reclamation addresses.
- ✗
Run the VACUUM command to reclaim disk space.
Why it's wrong here
VACUUM reclaims space from deleted rows and re-sorts, but the slow queries stem from high disk I/O on scans, which VACUUM does not reduce. It suits tables with heavy delete or update churn; here sort keys or distribution keys that prune scanned blocks are needed.
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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.