DBS-C01 Neptune Explain Plan Practice Question
A company is using Amazon Neptune to run graph queries. The cluster has one writer and two reader instances. After a major version upgrade, the query performance degrades for complex traversal queries. The database specialist suspects that the query optimizer is not using indexes effectively. Which action should the specialist take to identify the issue?
⚠ Common exam trap
The trap is that adding readers or checking metrics might seem helpful for performance, but the question specifically asks to identify index usage—only the explain plan provides that insight.
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
✓
Enable the Neptune explain plan feature and review the output.
Enabling the Neptune explain plan feature provides detailed information about how queries are executed, including index usage. This helps identify if the query optimizer is failing to use indexes effectively after the upgrade. Option A is incorrect because dropping and recreating indexes is unnecessary and disruptive; indexes are automatically maintained. Option C is incorrect because adding reader instances distributes read load but does not fix query optimization issues. Option D is incorrect because CloudWatch metrics show system-level performance, not query execution details.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Drop and recreate all indexes to ensure they are up to date.
Why it's wrong here
Recreating indexes may not change optimizer behavior.
- ✓
Enable the Neptune explain plan feature and review the output.
Why this is correct
Explain plan shows query execution steps and index usage.
- ✗
Add more reader instances to distribute the query load.
Why it's wrong here
This addresses load, not query optimization.
- ✗
Check the CloudWatch metrics for CPU utilization and query latency.
Why it's wrong here
Metrics indicate symptoms, not root cause of index usage.
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