domain-fintech_skill

Overview

This skill captures FinTech domain constraints and concrete Rust design guidance for building secure, auditable financial systems. It focuses on precision, immutability, transaction boundaries, and reproducibility to meet regulatory and correctness requirements. The content maps rules to Rust patterns, crates, and coding patterns that enforce financial guarantees.

How this skill works

The skill inspects domain rules (precision, audit trail, consistency) and translates them into implementation constraints and idiomatic Rust choices. It recommends crates (rust_decimal, chrono, uuid, serde) and patterns (value objects, newtypes, event sourcing, RAII transaction scopes) to ensure deterministic, traceable behavior. It highlights common pitfalls and gives small code patterns for Amount and ledger design.

When to use it

• Building payment, ledger, or trading systems that handle real money
• Designing transaction processing with strict audit and traceability requirements
• Enforcing exact monetary arithmetic and preventing precision loss
• Sharing immutable transaction data across threads or services
• Implementing double-entry accounting and validated balances

Best practices

• Never use floating-point (f32/f64) for money—use rust_decimal::Decimal or a validated newtype
• Model money as a typed value object (Amount/Currency) to prevent currency mixing
• Keep transactions immutable and traceable—use event sourcing and share with Arc<T>
• Use RAII or explicit transaction scope types to enforce atomic boundaries
• Perform checked arithmetic and validation to avoid silent overflows and inconsistencies
• Log structured events with trace IDs and serialize with serde for auditability

Example use cases

• Implementing a settlement engine that must preserve cent-level precision and full audit logs
• Designing a ledger with double-entry bookkeeping to guarantee money conservation
• Creating thread-safe immutable transaction records shared across services via Arc
• Building APIs that validate currency and amount types to avoid accidental currency mixing
• Instrumenting financial flows with structured tracing for compliance and dispute resolution