financial-systems-patterns

Double-entry bookkeeping requires immutable, balanced ledger entries that enforce the debits equal credits invariant to catch data corruption or software bugs. This skill provides the design patterns to construct a ledger that strictly maintains this fundamental accounting balance.

Preventing duplicate charges requires adding idempotency keys to your payment processing endpoints to ensure the same request is not executed twice. This skill outlines how to design idempotent payment flows and enforce strict state machines to avoid illegal transaction status transitions.

Avoiding rounding mistakes involves storing all monetary values as ISO 4217 minor units rather than floating-point numbers. This skill provides the patterns for multi-currency value storage and immutable ledger entries to maintain precise financial calculations.

Building a compliant financial audit trail requires constructing append-only records that meet PCI-DSS and SOC 2 regulatory requirements. This skill provides patterns to implement immutable audit logs and velocity-based fraud detection pipelines to block suspicious transactions.

Reconciling internal records with external settlements requires building reconciliation workflows to match your ledger against processor settlement reports. This skill provides patterns to design these workflows, ensuring your internal financial data aligns with external payment processor records.