financial-systems-patterns

What problem does it solve?

Building financial systems for payment processing, ledger management, and monetary transactions carries high risk of costly errors like rounding mistakes, duplicate charges, unbalanced books, and non-compliant audit trails that can lead to financial loss or regulatory penalties.

Core Features & Use Cases

• Double-Entry Bookkeeping: Implement immutable, balanced ledger entries that enforce the debits = credits invariant to catch corruption or bugs.
• Payment Processing Guardrails: Add idempotency keys to prevent duplicate charges, enforce strict payment state machines to avoid illegal status transitions, and build reconciliation workflows to match internal records with processor settlement reports.
• Compliance & Fraud Prevention: Construct append-only audit trails meeting PCI-DSS and SOC 2 requirements, and implement velocity-based fraud detection pipelines to block suspicious transactions.
• Use Case: For a new payment gateway, use this skill to design a ledger that stores all monetary values as ISO 4217 minor units, add idempotent payment endpoints, and set up nightly reconciliation against Stripe settlement reports.

Quick Start

Use the financial-systems-patterns skill to implement a double-entry ledger and idempotent payment processing flow for your new payment gateway.