DEA-C01 Data Operations and Support Practice Question
A company's Amazon Redshift cluster is running slowly. The data engineer suspects that table design is the cause. Which TWO design practices can improve query performance? (Choose TWO.)
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
✓
Define appropriate sort keys on frequently filtered columns.
Options A and C are correct. Defining appropriate sort keys on frequently filtered columns allows Redshift to use zone maps to skip irrelevant blocks, reducing the amount of data scanned. Defining appropriate distribution keys to collocate data on the same node slices minimizes data shuffling during joins, improving performance. Option B is incorrect because GROUP BY and DISTINCT are query optimization techniques, not table design practices. Option D is incorrect because resizing the cluster (adding nodes or slices) is an infrastructure change, not a table design practice. Option E is incorrect because using VARCHAR instead of CHAR for fixed-length strings does not directly impact query performance from a table design perspective; it is a data type choice that affects storage but not query performance via sort or distribution design.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Define appropriate sort keys on frequently filtered columns.
Why this is correct
Sort keys minimize the number of blocks scanned.
- ✗
Use GROUP BY instead of DISTINCT in queries.
Why it's wrong here
This is a query optimization, not a table design practice.
- ✓
Define appropriate distribution keys to collocate joins.
Why this is correct
Distribution keys reduce data shuffling across nodes.
- ✗
Increase the number of slices per node by resizing the cluster.
Why it's wrong here
Resizing is an operational change, not a table design practice.
- ✗
Use VARCHAR instead of CHAR for fixed-length strings.
Why it's wrong here
VARCHAR and CHAR have similar performance; this is not a major design improvement.
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Written by Johnson Ajibi, MSc IT Security
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