AdvancedTechnical
5 min
Database Index Optimization
DatabasesPerformance TuningSQL
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Interview Question
How do you design and optimize database indexes for query performance without over-indexing?
Key Points to Cover
- Analyze queries using EXPLAIN/EXPLAIN ANALYZE
- Choose composite indexes carefully
- Avoid redundant or unused indexes
- Consider write overhead and storage cost
- Regularly monitor index usage metrics
Evaluation Rubric
Uses query analysis tools30% weight
Designs optimal indexes30% weight
Balances performance vs overhead20% weight
Monitors index usage20% weight
Hints
- 💡Covering indexes, partial indexes, index-only scans.
Common Pitfalls to Avoid
- ⚠️Creating indexes on columns with very low cardinality (high number of duplicate values) as they offer little filtering benefit.
- ⚠️Ignoring the order of columns in composite indexes, leading to inefficient index utilization.
- ⚠️Over-indexing by creating an index for every query or column, forgetting the write overhead.
- ⚠️Failing to regularly review and prune unused or redundant indexes.
- ⚠️Not considering the impact of index fragmentation and using index maintenance tools.
Potential Follow-up Questions
- ❓How to detect unused indexes?
- ❓When are composite indexes useful?
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