ACID-compliant PostgreSQL double-entry ledgers, Fastify REST APIs with idempotency keys, AES-256 field-level encryption, Document AI neural OCR, and Redis message queue workers.
1. Double-Entry Accounting & ACID Relational Integrity
Financial software requires zero room for balance discrepancies. A double-entry accounting ledger is an immutable database record where every transaction contains at least one debit and one credit of equal amounts.
Using PostgreSQL atomic transaction blocks (`BEGIN ... COMMIT`) and row-level locking helps ensure that simultaneous credit transfers maintain ledger balance integrity and minimize race conditions.
- Total debits must equal total credits in every single transaction block.
- Ledger entries must be append-only with zero in-place updates or deletions.
- Header-based idempotency keys ensure network retries never create duplicate transactions.
2. Banking API Integration & Webhook Handling
Banking core systems and payment gateways can experience transient network timeouts. Engineering resilient fintech software requires exponential backoff retries, Redis queue workers (BullMQ), and dead-letter queue inspection tools.
3. Data Security, KYC & Field-Level Encryption
Enforce AES-256 encryption for sensitive identifiers (Aadhaar, PAN, bank account numbers). Sensitive tokens must be stored in httpOnly secure cookies, and all API calls must be logged in tamper-evident audit trails.