Performance Optimization Guide

Core Principles

1. Use DTOs throughout - Avoid converting to entities until necessary
2. Cache autocomplete results - Preserve full DTO data for converters
3. Skip unnecessary operations - Use configuration and conditional logic
4. Defer expensive operations - Move to background or later in workflow

Autocomplete Optimization (85-90% improvement)

Key pattern from Pharmacy Retail Sale (639ms -> 50ms):

1. Enhance DTO with fields needed for lightweight entity creation
2. Cache autocomplete results in controller for converter reuse
3. Skip discount calculations when no discount scheme active
4. Defer item instructions loading to later in workflow

Query Optimization

• Use DTO constructor queries instead of entity queries for display
• Always include retired = false in WHERE clauses
• Use indexed columns in WHERE and ORDER BY
• Add pagination to limit result sets
• Use JPQL aggregation (SUM, COUNT, GROUP BY) instead of Java loops

MySQL Performance

• Enable slow query log for queries > 1 second
• Use EXPLAIN to analyze query plans
• Add indexes for frequently queried columns
• Consider covering indexes for common queries

Report Optimization

• Use DTO queries for report data
• Pre-aggregate data in queries instead of Java
• Implement lazy loading for large datasets
• Cache report results when data doesn't change frequently

For detailed guides, read:

• Autocomplete Optimization
• MySQL Performance
• Performance Plan