Event Sourcing over CRUD for Financial Transaction Audit Trail

The team decided to replace standard CRUD in PostgreSQL with Event Sourcing for the financial transaction audit trail. Rationale: CRUD overwrites previous states on updates, making it impossible to provide compliance with historical change information (e.g., who changed transaction #8821 status from pending to approved). Database triggers were considered but rejected because they only capture row-level changes without business context (the why behind changes). Event Sourcing stores immutable domain events (TransactionCreated, TransactionApproved, StatusUpdated) in Kafka, with a materialized view in Postgres for fast frontend reads. This satisfies compliance requirements by preserving full audit history with business context. Reference architecture: Martin Fowlers Event Sourcing Pattern article. Implementation files: src/services/transactionService.ts (event producers), src/events/eventStore.ts (consumer/store logic).