### Transactions

The application uses database transactions in several key operations:

• Invoice creation: When creating a new invoice, a transaction ensures that both the invoice and its items are created atomically
• Status updates: Invoice status changes are handled within transactions to maintain data consistency
• Client updates: When updating client information, related operations are wrapped in transactions

Transactions are implemented in the following files:

• src/app/api/invoices/[id]/route.ts: For updating and deleting invoices
• src/app/api/invoices/route.ts: For creating new invoices

### Triggers

The system implements a sophisticated trigger system for invoice management:

• invoice_status_update_trigger: Automatically fires when an invoice status changes
  • Logs status changes in InvoiceStatusHistory
  • Creates notifications in InvoiceNotifications
  • Updates client status based on payment history
  • Automatically extends due dates when needed
  • Calculates and updates financial metrics

The trigger is implemented in sql/01_invoice_status_trigger.sql.

### Indexes

Several optimized indexes are implemented for better query performance:

• Client email lookups:
  • idx_client_email: Basic email search optimization
  • idx_client_email_tenant: Composite index for tenant-specific email searches
  • idx_client_email_lower: Case-insensitive email searches
• Invoice management:
  • idx_invoice_status_history_invoice_id: Optimizes status history lookups
  • idx_invoice_status_history_changed_at: Improves date-based queries
  • idx_invoice_notifications_invoice_id: Speeds up notification retrieval
  • idx_invoice_notifications_processed: Partial index for unprocessed notifications