LedgerConcurrency · Idempotency · Observability

A ledger is not just another CRUD app.

Recording transactions is the easy part. A trustworthy ledger must guarantee:

• Double-entry accounting · AtomicityMoney is never created or lost.Balanced postings and one database commit keep each movement whole.
• Concurrency controlAn account cannot be overspent.Row locks and available-balance checks prevent simultaneous requests from spending the same funds.
• IdempotencyRetries do not duplicate transactions.The same request key returns the original outcome instead of moving money twice.
• Audit trail · ObservabilityEvery movement is auditable.Trace each transaction's processing across services.
• Transactional outbox · Idempotent consumptionDownstream systems can process events reliably.The outbox preserves committed events for at-least-once delivery.