Financial Ledger Platform

Summary

A strict consistency financial architecture for double-entry accounting, payment processing, and audit trail management where every debit must have a corresponding credit, every state transition must be ordered and durable, and the complete history must be reconstructable without gaps. Event sourcing provides an append-only audit log; the outbox pattern guarantees at-least-once downstream event delivery without distributed two-phase commit (idempotent consumers deduplicate on event ID for effectively-once processing); PostgreSQL provides ACID guarantees for ledger entry atomicity.

Problem Statement

Financial systems cannot tolerate lost writes, phantom reads, or inconsistent account balances. A payment that debits one account must credit another within the same atomic transaction. An audit trail must capture every state transition, not just the current state. Concurrent balance updates must not interleave partial writes. The architecture must guarantee that every ledger entry is durable before acknowledging success to the caller, and that all downstream systems (notifications, analytics, reconciliation) receive every event at least once, deduplicating on a stable event ID.