Event Sourcing over CRUD for Audit Trails

Decision: Adopt Event Sourcing over standard CRUD for financial transaction audit trails. Problem: PostgreSQL updates overwrite previous states, losing compliance history (e.g., transaction #8821 status changes). Alternative considered: database triggers — rejected because they only capture row changes without business context (who changed it and why). Final decision: Use Kafka as the immutable event log for domain events (TransactionCreated, TransactionApproved, StatusUpdated) and build a Postgres materialized view for fast frontend reads. Reference architecture: Martin Fowler's 'Event Sourcing Pattern' article. Implementation scope: src/services/transactionService.ts (event producers), src/events/eventStore.ts (consumer/store logic). Rationale: Satisfies compliance audit requirements by preserving full business context of state changes.