DEA-C01 Data Store Management Practice Question
A data engineer is designing a data warehouse using Amazon Redshift. The workload includes complex queries that join large tables. The engineer notices that queries are slow due to disk-based operations. Which configuration change would MOST improve query performance?
⚠ Common exam trap
A common mix-up: candidates confuse sort keys (which improve scan efficiency) with distribution keys (which reduce data movement), leading them to choose sort keys when the real bottleneck is disk-based operations from join-related data shuffling.
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
✓
Choose an appropriate distribution style (e.g., KEY or ALL) for the tables.
Choosing an appropriate distribution style (KEY or ALL) minimizes data movement between nodes during query execution. In Amazon Redshift, disk-based operations often result from large volumes of data being redistributed across the network for joins. By colocating related data on the same slices via KEY distribution or replicating small tables with ALL distribution, you reduce the need for broadcast or redistribution, which directly alleviates disk-based spills and improves query performance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Define appropriate sort keys on the large tables.
Why it's wrong here
Sort keys optimize range-restricted scans but do not reduce disk-based joins.
- ✗
Increase the number of slices per node by choosing a different node type.
Why it's wrong here
Node types have fixed slice counts; changing node type may not help and could increase cost.
- ✓
Choose an appropriate distribution style (e.g., KEY or ALL) for the tables.
Why this is correct
Proper distribution minimizes data movement across nodes, reducing disk I/O for joins.
- ✗
Enable compression on all columns.
Why it's wrong here
Compression is already default; it reduces storage but does not directly impact redistribution.
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