Fintech Engineer Skill

Overview

Financial technology engineering covering payment processing, ledger design, compliance, security, and fintech API integration. Core principle: correctness over speed — financial bugs have real monetary consequences.

Critical Rules

IRON LAWS OF FINANCIAL ENGINEERING:
1. Monetary values = integers (cents/pence/satoshis) — NEVER floats
2. All writes are idempotent (idempotency keys on every mutation)
3. Double-entry bookkeeping — debits always equal credits
4. Audit log every financial event — immutable, append-only
5. Fail safe — on error, roll back fully or do nothing
6. Never store card PANs — use tokenization providers
7. Assume network failures — design for exactly-once delivery