Database Indexing Strategies for High Performance

Database indexing is one of the most powerful tools for optimizing query performance. Understanding when and how to create indexes can mean the difference between millisecond and second-long query times.

Understanding Database Indexes

An index is a data structure that improves the speed of data retrieval operations on a database table. Think of it as a book's index that helps you quickly find specific information.

Types of Indexes

1. Primary Index (Clustered)

One per table - Determines physical storage order
Automatically created - Usually on primary key
Fast lookups - Direct access to data pages

2. Secondary Index (Non-Clustered)

Multiple per table - Points to primary key or row location
Flexible creation - On any column combination
Additional storage - Requires extra disk space

3. Composite Index

Index Design Principles

The 80/20 Rule

Focus on indexing columns that appear in:

WHERE clauses (80% of performance gains)
ORDER BY clauses
JOIN conditions
GROUP BY clauses

Column Order Matters

For composite indexes, order columns by:

Equality conditions first
Range conditions second
Sort order last

Performance Impact Analysis

Before Indexing

After Indexing

Advanced Indexing Strategies

Partial Indexes

Index only relevant rows to save space:

Covering Indexes

Include all needed columns to avoid table lookups:

Function-Based Indexes

Index computed values:

Index Maintenance

Monitor Index Usage

Remove Unused Indexes

Unused indexes hurt performance:

Slow INSERT/UPDATE/DELETE operations
Waste storage space
Increase maintenance overhead

Common Pitfalls

Over-Indexing

Every column doesn't need an index
Composite indexes can serve multiple queries
Monitor write performance impact

Under-Indexing

Missing indexes on foreign keys
No indexes on frequently filtered columns
Ignoring query execution plans

Best Practices Checklist

✅ Analyze query patterns before creating indexes
✅ Use EXPLAIN plans to verify index usage
✅ Monitor index performance regularly
✅ Consider composite indexes for multi-column queries
✅ Remove unused indexes periodically
✅ Test index impact on write operations

Conclusion

Effective indexing is both art and science. Start with your most frequent queries, measure performance impact, and iterate based on real-world usage patterns.

Remember: The best index is the one that's actually used by your queries.