Fintech Engineering Handbook

The Fintech Engineering Handbook is a resource guide for software engineers working with financial systems, outlining essential patterns and principles to ensure trustworthy money systems. It establishes three core principles: preventing invented data through idempotency and reconciliation, preventing lost data through precision and audit trails, and maintaining zero trust through verification and cross-checking. The handbook emphasizes critical decisions like precision handling in monetary representation, recommending against floating-point arithmetic and instead advocating for arbitrary precision, minor-units precision (storing amounts as integers), or rational numbers depending on the system's requirements.