Explain PostgreSQL performance tuning best practices.

Configuration Tuning:
• shared_buffers (25% of RAM)
• effective_cache_size (75% of RAM)
• work_mem (per operation)
• maintenance_work_mem (for VACUUM)

Query Optimization:
• Use EXPLAIN ANALYZE
• Proper indexing strategy
• Avoid SELECT *
• Use prepared statements

Index Optimization:
• Create indexes on WHERE clauses
• Composite indexes for multiple columns
• Partial indexes for filtered data
• Regular REINDEX for maintenance

Maintenance:
• Regular VACUUM and ANALYZE
• Monitor table bloat
• Update statistics
• Archive old WAL files