Double-entry ledger service for escrow payments

We need an experienced backend engineer to design and build an immutable, double-entry ledger that records escrow funding, milestone releases, refunds, and platform fees. The service must be idempotent, auditable, and reconcilable. Deliverables include the schema, transaction APIs, idempotency handling, and a reconciliation report. Strong PostgreSQL and payments background required.

1. 1. Describe a ledger or payments system you've built.