Domain Fintech

This one maps fintech domain constraints directly to Rust design decisions. It's built around the core truth that you can't use f64 for money, ever, and shows you how immutability, precision, and audit trails flow down from regulatory requirements into concrete patterns like rust_decimal newtypes and Arc for transaction records. The trace-down tables connect "need immutable transaction records" to specific ownership choices and crate selections. Most valuable when you're starting a payment system or trading platform and need to see why certain architectural choices aren't optional in finance. The currency type example and common mistakes section will save you from the classic blunders.

skills.sh installs: 3K
GitHub stars: 1.6K
last updated: Aug 21, 2026

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Install

$ npx -y skills add actionbook/rust-skills --skill domain-fintech --agent claude-code

Installs into .claude/skills of the current project.

Files

FinTech Domain

Layer 3: Domain Constraints

Domain Constraints → Design Implications

Domain Rule	Design Constraint	Rust Implication
Audit trail	Immutable records	Arc, no mutation
Precision	No floating point	rust_decimal
Consistency	Transaction boundaries	Clear ownership
Compliance	Complete logging	Structured tracing
Reproducibility	Deterministic execution	No race conditions

Critical Constraints

Financial Precision

RULE: Never use f64 for money
WHY: Floating point loses precision
RUST: Use rust_decimal::Decimal

Audit Requirements

RULE: All transactions must be immutable and traceable
WHY: Regulatory compliance, dispute resolution
RUST: Arc<T> for sharing, event sourcing pattern

Consistency

RULE: Money can't disappear or appear
WHY: Double-entry accounting principles
RUST: Transaction types with validated totals

Trace Down ↓

From constraints to design (Layer 2):

"Need immutable transaction records"
    ↓ m09-domain: Model as Value Objects
    ↓ m01-ownership: Use Arc for shared immutable data

SKILL.md on GitHub

Details

Repository: github.com/actionbook/rust-skills
Categories: Rust, Finance & Trading
First seen: Jun 3, 2026