The correct answer is to use DISTKEY on the join column to co-locate data, as this directly addresses the core bottleneck in Redshift join performance optimization. When you set the distribution style to KEY on the column used in frequent joins, Redshift physically places rows with the same join key value on the same compute node, enabling a collocated join that avoids the expensive redistribution of data across the network during query execution. On the AWS Certified Data Engineer Associate DEA-C01 exam, this concept tests your understanding of how data distribution strategies directly impact query performance in a massively parallel processing environment; a common trap is choosing SORT KEY instead, which only optimizes data skipping and filtering, not join co-location. Remember the memory tip: “KEY for co-location, SORT for ordering”—if you need to join fast, distribute on the join column.
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.
A company is using Amazon Redshift for a data warehouse. The data engineer needs to improve query performance for a table that is frequently joined with other tables on a specific column. Which THREE actions would help improve join performance? (Choose THREE.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set the distribution style to KEY on the join column
Setting the distribution style to KEY on the join column (option A) ensures that rows with the same join key value are co-located on the same compute node. This allows Redshift to perform a collocated join, avoiding the expensive redistribution of data across the network during query execution, which significantly improves join performance.
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.
✓
Set the distribution style to KEY on the join column
Why this is correct
This is the same as option C; it co-locates data for joins.
Related concept
Read the scenario before looking for a memorised answer.
✓
Apply a SORTKEY on the join column
Why this is correct
A SORTKEY allows Redshift to use zone maps to skip blocks that don't match the join condition.
Related concept
Read the scenario before looking for a memorised answer.
✓
Use DISTKEY on the join column to co-locate data
Why this is correct
Distributing by the join column ensures that matching rows are on the same node, reducing data movement.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use DISTSTYLE ALL to replicate the table to all nodes
Why it's wrong here
DISTSTYLE ALL is for small dimension tables; for large fact tables, it is inefficient.
✗
Change the column data type to a fixed-length CHAR
Why it's wrong here
Data type changes do not significantly impact join performance.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse DISTSTYLE ALL (option D) as a required action for join performance, but the question asks for three specific actions, and DISTSTYLE ALL is a valid but separate optimization not listed among the correct three; the exam expects you to recognize that A, B, and C are the correct trio, with D being a distractor that is also correct in isolation but not part of the required set.
Detailed technical explanation
How to think about this question
Under the hood, Redshift distributes table rows across nodes based on the distribution style. With KEY distribution, the hash of the join column determines the node, ensuring that matching join keys from both tables land on the same slice. The SORTKEY (option B) further accelerates joins by allowing Redshift to skip irrelevant blocks via zone maps, reducing the amount of data scanned. DISTKEY (option C) is synonymous with setting distribution style to KEY, so it is essentially the same action as option A—both co-locate data for the join column.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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: Set the distribution style to KEY on the join column — Setting the distribution style to KEY on the join column (option A) ensures that rows with the same join key value are co-located on the same compute node. This allows Redshift to perform a collocated join, avoiding the expensive redistribution of data across the network during query execution, which significantly improves join performance.
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
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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. A company is running a data warehouse on Amazon Redshift. The data engineering team notices that query performance has degraded over time. They suspect that data distribution is causing excessive data movement between nodes. The table is joined frequently on the customer_id column. Which column should be chosen as the distribution key to optimize join performance?
medium
A.AUTO distribution
✓ B.customer_id
C.order_date
D.EVEN distribution
Why B: The correct answer is B (customer_id) because Redshift distributes data across nodes based on the distribution key. When two tables are joined on customer_id, using it as the distribution key ensures that matching rows from both tables are co-located on the same node, eliminating the need for data redistribution (broadcast or shuffle) during the join. This minimizes network traffic and reduces query latency, directly addressing the performance degradation caused by excessive data movement.
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.