Event Sourcing over CRUD for Audit Trails

The team decided to move from standard CRUD operations in PostgreSQL to Event Sourcing for financial transaction audit trails. Previously, updates in PostgreSQL would overwrite previous states, making it impossible to provide compliance history (e.g., who changed transaction #8821 from pending to approved). The alternative of using a history_logs table with database triggers was rejected because triggers lose business context - they see row changes but not the reason or user intent behind the change. The chosen approach uses Kafka to store an immutable event log (TransactionCreated, TransactionApproved, StatusUpdated) with a materialized view in Postgres for fast reads. Reference: Martin Fowler's Event Sourcing Pattern article. Implementation files: src/services/transactionService.ts and src/events/eventStore.ts.