The answer is to define appropriate sort keys and apply compression encodings to columns. Sort keys improve Amazon Redshift query performance by physically co-locating rows with similar values on disk, which allows the query optimizer to use zone maps to skip irrelevant data blocks during table scans, reducing I/O and speeding up range-restricted queries and merge joins. Compression encodings further reduce storage footprint and the amount of data read from disk, making scans faster. On the AWS Certified Data Engineer Associate DEA-C01 exam, this question tests your understanding of Redshift’s physical design choices; a common trap is to confuse sort keys with distribution keys or to think that compression only saves storage without affecting query speed. Remember the memory tip: “Sort to skip, compress to shrink”—sort keys let you skip blocks, compression shrinks what you read.
DEA-C01 Data Store Management Practice Question
This DEA-C01 practice question tests your understanding of data store management. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which TWO actions can help improve query performance in Amazon Redshift? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use appropriate sort keys for tables.
Option A is correct because defining appropriate sort keys in Amazon Redshift enables the query optimizer to use zone maps to skip irrelevant data blocks during table scans, significantly reducing the amount of data read from disk. Sort keys also improve the effectiveness of merge joins and the performance of range-restricted queries by physically co-locating rows with similar sort key values on disk.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Use appropriate sort keys for tables.
Why this is correct
Sort keys help the query optimizer scan less data.
Related concept
Read the scenario before looking for a memorised answer.
Use VARCHAR instead of CHAR for fixed-length strings.
Why it's wrong here
Choosing data type is not a primary performance improvement technique.
✓
Apply compression encodings to columns.
Why this is correct
Compression reduces storage and I/O, improving performance.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the number of nodes in the cluster.
Why it's wrong here
Scaling up may help but is not always the solution and adds cost.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume scaling out (adding nodes) always speeds up individual queries, but in Redshift, query performance is more dependent on data layout (sort keys, distribution, compression) than on cluster size, and adding nodes primarily benefits concurrent workloads rather than single-query latency.
Detailed technical explanation
How to think about this question
Under the hood, Amazon Redshift stores data in 1 MB blocks, and each block's minimum and maximum values are recorded in zone maps. When a query includes a filter on a sort key column, Redshift uses these zone maps to eliminate entire blocks that do not contain relevant data, a process known as block-level pruning. Compression encodings (Option D) further reduce the amount of data read from disk per block, and when combined with sort keys, they can dramatically reduce I/O and improve query response times, especially in large fact tables with range-based filters.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Data Store Management — This question tests Data Store Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use appropriate sort keys for tables. — Option A is correct because defining appropriate sort keys in Amazon Redshift enables the query optimizer to use zone maps to skip irrelevant data blocks during table scans, significantly reducing the amount of data read from disk. Sort keys also improve the effectiveness of merge joins and the performance of range-restricted queries by physically co-locating rows with similar sort key values on disk.
What should I do if I get this DEA-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which TWO actions can improve query performance on an Amazon Redshift cluster? (Choose two.)
medium
✓ A.Define appropriate sort keys
B.Increase the number of nodes
C.Use EVEN distribution style for all tables
✓ D.Use columnar compression
E.Run VACUUM command regularly
Why A: Options A and B are correct because sort keys improve data organization and compression reduces I/O. Option C (distribution style) affects data distribution but not directly query performance. Option D (increasing number of nodes) adds cost. Option E (vacuum) reclaims space but does not directly improve query speed.
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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.
Question Discussion
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