The answer is DISTSTYLE ALL, which forces the entire table onto a single slice per node, causing the query to use only one slice instead of all available slices. In Amazon Redshift, each node is divided into slices based on CPU cores—dc2.large nodes have two slices each—but DISTSTYLE ALL replicates a full copy of the table to every node and stores that copy on just one slice per node, so a full table scan cannot parallelize across multiple slices. On the AWS Certified Data Engineer Associate DEA-C01 exam, this question tests your understanding of how distribution styles impact query parallelism; a common trap is confusing DISTSTYLE ALL with EVEN or KEY, which spread data across slices. Remember the memory tip: “ALL on one slice per node” to recall that while the table is on every node, it’s locked to a single slice, limiting slice-level parallelism.
DEA-C01 Data Operations and Support Practice Question
This DEA-C01 practice question tests your understanding of data operations and support. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 data engineer is troubleshooting an Amazon Redshift cluster that is running slowly. The cluster has 4 dc2.large nodes. The engineer runs a query that scans a large table and notices that the query uses only a single slice instead of all slices. The table is distributed with DISTSTYLE ALL. What is the most likely reason for the query using only one slice?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The table uses DISTSTYLE ALL, which stores the entire table on a single slice per node.
Option B is correct because DISTSTYLE ALL means the entire table is copied to every node, but within each node, the data is stored on a single slice. Redshift slices are determined by the number of cores per node; for dc2.large nodes, there are 2 slices per node. However, with DISTSTYLE ALL, each node stores a full copy of the table, but the table is not distributed across slices; it is replicated to each node, and queries may not parallelize across slices efficiently. Actually, with DISTSTYLE ALL, the table is replicated to all nodes, but within each node, the data is stored on a single slice (the leader node assigns the table to one slice per node). So queries that scan the entire table may only use one slice per node, leading to underutilization. Option A is wrong because the sort key affects data ordering, not slice utilization. Option C is wrong because WLM queues affect concurrency, not slice usage. Option D is wrong because the query is not using a single node but multiple nodes, but only one slice per node.
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.
✗
The query is running on the leader node instead of the compute nodes.
Why it's wrong here
The leader node distributes queries to compute nodes; the query is running on compute nodes but only one slice per node.
✓
The table uses DISTSTYLE ALL, which stores the entire table on a single slice per node.
Why this is correct
DISTSTYLE ALL replicates the table to each node, but it is stored on one slice per node, limiting parallelism.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The workload management (WLM) queue is configured with a single query slot.
Why it's wrong here
WLM queue slots affect concurrent query execution, not slice utilization for a single query.
✗
The table does not have a sort key defined.
Why it's wrong here
Missing sort key affects performance but does not cause single-slice usage.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 DEA-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Data Operations and Support — This question tests Data Operations and Support — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The table uses DISTSTYLE ALL, which stores the entire table on a single slice per node. — Option B is correct because DISTSTYLE ALL means the entire table is copied to every node, but within each node, the data is stored on a single slice. Redshift slices are determined by the number of cores per node; for dc2.large nodes, there are 2 slices per node. However, with DISTSTYLE ALL, each node stores a full copy of the table, but the table is not distributed across slices; it is replicated to each node, and queries may not parallelize across slices efficiently. Actually, with DISTSTYLE ALL, the table is replicated to all nodes, but within each node, the data is stored on a single slice (the leader node assigns the table to one slice per node). So queries that scan the entire table may only use one slice per node, leading to underutilization. Option A is wrong because the sort key affects data ordering, not slice utilization. Option C is wrong because WLM queues affect concurrency, not slice usage. Option D is wrong because the query is not using a single node but multiple nodes, but only one slice per node.
What should I do if I get this DEA-C01 question wrong?
Identify which DEA-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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