DEA-C01 Data Store Management Practice Question
A company uses Amazon Redshift for its data warehouse. The data engineer notices that queries are slow on a large table that is frequently filtered on a column 'transaction_date'. Which optimization technique best improves query performance?
⚠ Common exam trap
A common mix-up: candidates confuse distribution keys (which optimize joins) with sort keys (which optimize filtering and range scans), leading them to pick distribution key as the answer for a single-table filter performance issue.
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
✓
Set the sort key to 'transaction_date'.
Setting the sort key to 'transaction_date' organizes the table data physically by that column, which allows Redshift to use zone maps to skip blocks that don't match query filters. This dramatically reduces the amount of data scanned for range-restricted queries on 'transaction_date', improving query performance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Apply compression encoding to 'transaction_date'.
Why it's wrong here
Compression reduces storage but not query speed for range filters.
- ✓
Set the sort key to 'transaction_date'.
Why this is correct
Sort keys enable zone maps to skip irrelevant blocks.
- ✗
Set the distribution key to 'transaction_date'.
Why it's wrong here
Distribution key affects data distribution, not filtering performance.
- ✗
Run VACUUM on the table.
Why it's wrong here
VACUUM reclaims space and sorts, but does not directly improve filter performance if sort key is not set.
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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.