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 a slow-running Amazon Redshift query. The query involves a large fact table with a distribution style of EVEN and a sort key on date. The table has 10 slices. The engineer notices that the query is performing a broadcast join with a small dimension table. Which change would most improve performance?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change the fact table to DISTSTYLE KEY on the join column
Option C is correct because changing the fact table to KEY distribution on the join column reduces data movement. Option A is wrong because ALL distribution on the dimension table is better but not listed. Option B is wrong because it does not reduce the broadcast. Option D is wrong because removing sort key would hurt performance for range queries.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Remove the sort key and use a compound sort key on the join column
Why it's wrong here
Removing the sort key degrades performance for date-range queries.
✗
Change the dimension table to DISTSTYLE ALL
Why it's wrong here
ALL distribution copies the table to all nodes, reducing broadcast, but the question asks for fact table change.
✗
Increase the number of slices by resizing the cluster
Why it's wrong here
More slices may not reduce broadcast join cost.
✓
Change the fact table to DISTSTYLE KEY on the join column
Why this is correct
KEY distribution colocates matching rows, reducing the need for broadcast.
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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. Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets. 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.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DEA-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Data Operations and Support — This question tests Data Operations and Support — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Change the fact table to DISTSTYLE KEY on the join column — Option C is correct because changing the fact table to KEY distribution on the join column reduces data movement. Option A is wrong because ALL distribution on the dimension table is better but not listed. Option B is wrong because it does not reduce the broadcast. Option D is wrong because removing sort key would hurt performance for range queries.
What should I do if I get this DEA-C01 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DEA-C01 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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