The correct action is to add more nodes to the cluster. When a Redshift cluster’s disk space reaches 80% full, query performance degrades because Redshift relies on large sequential I/O operations; high disk utilization forces more random I/O and increases spilling to disk, which directly slows down query throughput. Adding nodes increases both storage and compute capacity, alleviating the I/O bottleneck and restoring performance. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of Redshift’s scaling mechanics and the critical 70-80% disk utilization threshold—a common trap is to consider only resizing existing nodes or cleaning up data, but the recommended fix for performance degradation due to full disk is horizontal scaling. Remember the memory tip: “80% full? Add nodes for the pull.”
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 uses Amazon Redshift for its data warehouse. The data engineer notices that queries are running slower than expected. The system administrator reports that the cluster's disk space is 80% full. Which action should the engineer take to improve query performance?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add more nodes to the cluster to increase storage and compute capacity.
When a Redshift cluster's disk space is 80% full, query performance degrades because Redshift relies on large sequential I/O operations, and high disk utilization forces more random I/O and increases the likelihood of spilling to disk. Adding nodes increases both storage capacity and compute resources, directly alleviating the I/O bottleneck and improving query throughput. This is the recommended scaling action when disk space exceeds 70-80% utilization.
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.
✗
Redesign the sort keys to optimize query performance.
Why it's wrong here
Sort keys improve query performance but do not address disk space.
✗
Run the VACUUM command to reclaim space.
Why it's wrong here
VACUUM reclaims space but does not increase total capacity.
✓
Add more nodes to the cluster to increase storage and compute capacity.
Why this is correct
Adding nodes increases both storage and compute, improving performance.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable concurrency scaling to handle more queries.
Why it's wrong here
Concurrency scaling adds compute resources, not storage.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the symptom (slow queries) with a need for sort key optimization or vacuuming, when the root cause is insufficient storage capacity causing I/O bottlenecks, which only adding nodes can resolve.
Detailed technical explanation
How to think about this question
Redshift stores data in 1 MB blocks and uses columnar compression; when disk is 80% full, the cluster's workload manager may begin spilling intermediate results to disk, dramatically increasing query latency. Adding nodes not only increases total storage but also adds more slices (each node has multiple slices), which improves parallelism for both reads and writes. In practice, monitoring disk space via STV_DISKUTIL and setting CloudWatch alarms at 70% utilization is a best practice to avoid performance degradation before scaling becomes necessary.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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: Add more nodes to the cluster to increase storage and compute capacity. — When a Redshift cluster's disk space is 80% full, query performance degrades because Redshift relies on large sequential I/O operations, and high disk utilization forces more random I/O and increases the likelihood of spilling to disk. Adding nodes increases both storage capacity and compute resources, directly alleviating the I/O bottleneck and improving query throughput. This is the recommended scaling action when disk space exceeds 70-80% utilization.
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 →
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.