Event Sourcing over CRUD for Financial Transaction Audit Trails

The team decided to replace the current CRUD pattern in PostgreSQL with Event Sourcing for financial transaction audit trails. Problem: CRUD updates overwrite previous states, making it impossible to trace who changed transaction statuses (e.g., status changed from pending to approved). Alternative considered: Database triggers and a history_logs table. Rejected because business context is lost — triggers only see row changes, not the user intent or reason for the change. Decision: Use Kafka to store immutable domain events (TransactionCreated, TransactionApproved, StatusUpdated), and build a materialized view in Postgres for fast reads on the frontend. Reference architecture: Martin Fowler's Event Sourcing Pattern article. Implementation: Event producers in src/services/transactionService.ts, consumer/store logic in src/events/eventStore.ts.