The correct answer is to run VACUUM, ANALYZE, and DEEP COPY regularly. VACUUM reclaims disk space from deleted or updated rows and re-sorts data when sort keys are defined, directly addressing the table bloat that degrades COPY command performance. ANALYZE updates table statistics so the query optimizer generates efficient execution plans, while DEEP COPY completely recreates the table to eliminate bloat more thoroughly than a standard VACUUM. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this question tests your understanding of Redshift maintenance operations in the context of data pipeline performance—a common trap is confusing UNLOAD (an export tool) or distribution style changes with routine maintenance. Remember that VACUUM and ANALYZE are lightweight, recurring tasks, while DEEP COPY is a heavier operation for severe bloat. Memory tip: think "VAD" for VACUUM, ANALYZE, DEEP COPY—the three pillars of Redshift housekeeping.
MLS-C01 Data Engineering Practice Question
This MLS-C01 practice question tests your understanding of data engineering. 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 to run analytics on sales data. The data is loaded daily from S3 using COPY commands. The team notices that the COPY command performance degrades over time due to table bloat. The team needs to maintain query performance and reduce storage costs. Which combination of maintenance operations should the team perform regularly? (Choose THREE.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Run the VACUUM command to reclaim space and re-sort rows.
Option A, C, and D are correct. VACUUM reclaims space and re-sorts rows (if sort keys defined). ANALYZE updates statistics for query planning. DEEP COPY recreates the table to eliminate bloat completely. Option B is wrong because UNLOAD exports data, not maintenance. Option E is wrong because changing distribution style is a schema change, not regular maintenance.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Run the UNLOAD command to export data to S3 and then reload.
Why it's wrong here
UNLOAD is for exporting, not for maintenance.
✗
Change the distribution style of the table to KEY.
Why it's wrong here
Changing distribution style is a schema modification, not a maintenance operation.
✓
Run the VACUUM command to reclaim space and re-sort rows.
Why this is correct
VACUUM removes deleted rows and re-sorts data.
Related concept
Static NAT maps one inside address to one outside address.
✓
Run a DEEP COPY to recreate the table with optimal physical storage.
Why this is correct
DEEP COPY eliminates bloat by creating a new table.
Related concept
Static NAT maps one inside address to one outside address.
✓
Run the ANALYZE command to update table statistics.
Why this is correct
ANALYZE ensures the query optimizer has up-to-date statistics.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related MLS-C01 NAT questions on configuration and troubleshooting.
Data Engineering — This question tests Data Engineering — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Run the VACUUM command to reclaim space and re-sort rows. — Option A, C, and D are correct. VACUUM reclaims space and re-sorts rows (if sort keys defined). ANALYZE updates statistics for query planning. DEEP COPY recreates the table to eliminate bloat completely. Option B is wrong because UNLOAD exports data, not maintenance. Option E is wrong because changing distribution style is a schema change, not regular maintenance.
What should I do if I get this MLS-C01 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related MLS-C01 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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