DEA-C01 Data Operations and Support Practice Question
A company runs an Amazon Redshift cluster for analytics. During peak hours, query performance degrades significantly. The data engineer notices that disk space usage is above 80% on many nodes. Which of the following is the MOST effective long-term solution to improve query performance?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Resize the cluster to include additional nodes.
Resizing the cluster to include additional nodes increases both storage and compute capacity, directly addressing the high disk usage and improving query performance. Increasing WLM queue slots (Option A) only manages concurrency but does not add capacity. Compression encoding (Option C) reduces storage but may not alleviate immediate performance degradation, and is not a long-term solution for capacity. Running VACUUM (Option D) reclaims space from deleted rows but does not add new capacity.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Increase the workload management (WLM) queue slots.
Why it's wrong here
Adding WLM queue slots changes query concurrency allocation, not disk capacity; with nodes above 80% full, queries still spill to disk and slow down. More slots suit concurrency contention with adequate storage, not a cluster whose bottleneck is disk space.
- ✓
Resize the cluster to include additional nodes.
Why this is correct
Adding nodes increases both storage capacity and compute parallelism across the cluster, relieving the 80% disk pressure while distributing query workload. This addresses the root cause of degradation rather than temporarily masking it, providing a durable performance improvement for peak-hour analytics.
- ✗
Apply compression encoding to all columns.
Why it's wrong here
Compression encoding reduces storage footprint and I/O, but it is applied at table creation or via ALTER, not as the remedy for an existing 80%-full cluster whose nodes spill to disk. It suits designing new tables or reducing scanned bytes, not reclaiming space already consumed.
- ✗
Run the VACUUM command to reclaim space.
Why it's wrong here
VACUUM reclaims space from deleted rows and re-sorts, giving temporary relief, but it does not add capacity and must be rerun as data grows. It suits tables with heavy delete/update churn, not sustained disk pressure needing a durable capacity or distribution fix.
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