Crate Structure

Overview

NanoARB is organized as a Cargo workspace with 7 crates, each responsible for a distinct layer of the trading system. This modular design enables:

Independent development - Crates can be tested and benchmarked in isolation
Clear dependencies - One-way dependency graph prevents circular references
Reusability - Core types and traits shared across all crates
Fast compilation - Changes to one crate don’t require rebuilding unrelated code

Dependency Graph

Dependency rule: All crates depend on nano-core, and dependencies only flow downward in the stack.

nano-core

Location: crates/nano-core/ Description: Foundation crate providing domain types, traits, constants, and error handling for the entire system.

Key Types

Price (`types/price.rs:1`)

Fixed-point decimal representation to avoid floating-point errors:

#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct Price {
    raw: i64,  // In minimum price increments (ticks)
}

impl Price {
    pub fn from_ticks(ticks: i64, tick_size: u32) -> Self;
    pub fn as_f64(&self, tick_size: f64) -> f64;
}

Usage: Price::from_ticks(50000, 25) represents $5000.00 with 0.25 tick size.

Quantity (`types/quantity.rs:1`)

#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct Quantity(u32);

Side (`types/side.rs:1`)

#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum Side {
    Buy,
    Sell,
}

Timestamp (`types/timestamp.rs:1`)

Nanosecond-precision timestamp:

#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct Timestamp(u64);  // Nanoseconds since epoch

impl Timestamp {
    pub fn now() -> Self;
    pub fn from_nanos(nanos: u64) -> Self;
    pub fn as_nanos(&self) -> u64;
}

Order (`types/order.rs:1`)

pub struct Order {
    pub id: OrderId,
    pub instrument_id: u32,
    pub side: Side,
    pub price: Price,
    pub quantity: Quantity,
    pub timestamp: Timestamp,
    pub order_type: OrderType,
}

Core Traits

Defines interfaces for all major system components (see traits.rs:1):

Strategy (`traits.rs:48`)

pub trait Strategy: Send + Sync {
    fn name(&self) -> &str;
    fn on_market_data(&mut self, book: &dyn OrderBook) -> Vec<Order>;
    fn on_fill(&mut self, fill: &Fill);
    fn on_order_ack(&mut self, order_id: OrderId);
    fn position(&self) -> i64;
    fn pnl(&self) -> f64;
}

OrderBook (`traits.rs:6`)

pub trait OrderBook: Send + Sync {
    fn best_bid(&self) -> Option<(Price, Quantity)>;
    fn best_ask(&self) -> Option<(Price, Quantity)>;
    fn mid_price(&self) -> Option<Price>;
    fn spread(&self) -> Option<Price>;
}

ModelInference (`traits.rs:160`)

pub trait ModelInference: Send + Sync {
    type Input;
    type Output;
    fn predict(&self, input: &Self::Input) -> Result<Self::Output>;
    fn expected_latency_ns(&self) -> u64;
}

Dependencies

rust_decimal - Decimal arithmetic
serde / bincode / rkyv - Serialization
chrono - Time handling
thiserror - Error types

No runtime dependencies on other NanoARB crates.

nano-feed

Location: crates/nano-feed/ Description: CME MDP 3.0 binary protocol parser and synthetic data generator.

Features

SBE Decoder - Parses Simple Binary Encoding messages from CME
Zero-copy parsing - Uses nom combinator library for allocation-free parsing
Message types - Book updates, trades, channel resets, security status
Synthetic generator - Creates realistic market data for development and testing

Key Modules

MdpParser (`parser.rs:1`)

Parses raw CME MDP 3.0 packets:

pub struct MdpParser {
    // Internal state for incremental parsing
}

impl MdpParser {
    pub fn new() -> Self;
    pub fn parse(&mut self, data: &[u8]) -> Result<MdpMessage>;
}

Supported message types (see messages.rs:1):

MDIncrementalRefreshBook (Template 46) - Order book updates
MDIncrementalRefreshTrade (Template 42) - Executed trades
ChannelReset (Template 4) - Channel state reset
SecurityStatus (Template 30) - Trading status changes

Synthetic Data Generator (`synthetic.rs:1`)

Generates realistic market microstructure:

pub struct SyntheticFeedGenerator {
    pub base_price: f64,
    pub volatility: f64,
    pub spread_bps: f64,
    pub tick_rate_hz: f64,
}

impl SyntheticFeedGenerator {
    pub fn generate_tick(&mut self, timestamp: Timestamp) -> BookUpdate;
}

Generation model:

Geometric Brownian Motion for price drift
Poisson arrivals for order events
Realistic bid/ask spread and depth
Correlated buy/sell pressure

Dependencies

nano-core - Core types
nom - Parser combinators
bytes - Byte manipulation
rand / rand_distr - Random number generation

nano-lob

Location: crates/nano-lob/ Description: High-performance limit order book with 20-level depth and HFT feature extraction.

Key Modules

OrderBook (`orderbook.rs:1`)

pub struct OrderBook {
    instrument_id: u32,
    bids: BTreeMap<Price, Quantity>,
    asks: BTreeMap<Price, Quantity>,
    timestamp: Timestamp,
}

impl OrderBook {
    pub fn new(instrument_id: u32) -> Self;
    pub fn apply_update(&mut self, update: &BookUpdate);
    pub fn best_bid(&self) -> Option<(Price, Quantity)>;
    pub fn best_ask(&self) -> Option<(Price, Quantity)>;
    pub fn mid_price(&self) -> Option<Price>;
}

Performance (see benchmarks in benches/orderbook.rs):

Update operation: 45ns median (P95: 62ns)
BBO query: 5ns (read-only, no allocation)
20-level iteration: 180ns

LobFeatureExtractor (`features.rs:1`)

Extracts HFT features for ML models:

pub struct LobFeatureExtractor;

impl LobFeatureExtractor {
    pub fn microprice(book: &OrderBook) -> f64;
    pub fn order_flow_imbalance(book: &OrderBook) -> f64;
    pub fn vpin(snapshots: &[LobSnapshot]) -> f64;
    pub fn book_imbalance(book: &OrderBook, levels: usize) -> f64;
    pub fn extract_all(book: &OrderBook) -> Array1<f64>;
}

Feature definitions:

Microprice - Volume-weighted mid:

μ = (P_bid * Q_ask + P_ask * Q_bid) / (Q_bid + Q_ask)

Order Flow Imbalance (OFI):
OFI = Δ(Q_bid) - Δ(Q_ask)
VPIN - Volume-Synchronized Probability of Informed Trading:
VPIN = |V_buy - V_sell| / V_total
Book Imbalance:
BI = (Q_bid - Q_ask) / (Q_bid + Q_ask)

SnapshotRingBuffer (`snapshot.rs:1`)

Fixed-size circular buffer for LOB history:

pub struct SnapshotRingBuffer {
    snapshots: Vec<LobSnapshot>,
    capacity: usize,
    cursor: usize,
}

impl SnapshotRingBuffer {
    pub fn new(capacity: usize) -> Self;
    pub fn push(&mut self, snapshot: LobSnapshot);
    pub fn as_tensor(&self) -> Array2<f64>;  // (seq_len, features)
}

Usage: Maintain 100-snapshot history for ML model input.

Dependencies

nano-core - Core types and traits
nano-feed - Market data messages
ndarray - Tensor operations
smallvec - Stack-allocated vectors
parking_lot - Fast mutexes

nano-model

Location: crates/nano-model/ Description: ONNX-based ML model inference for trading signals.

Features

ONNX Runtime - Cross-platform inference engine
Model types - Mamba, Transformer, Decision Transformer, IQL
Batched inference - Process multiple instruments simultaneously
Latency tracking - Built-in performance monitoring

Key Types

SignalModel

pub struct SignalModel {
    // session: ort::Session,  // Commented due to ONNX version compatibility
    input_shape: Vec<usize>,
    output_shape: Vec<usize>,
}

impl ModelInference for SignalModel {
    type Input = Array2<f64>;  // (seq_len, features)
    type Output = Array2<f64>; // (horizons, classes)
    
    fn predict(&self, input: &Self::Input) -> Result<Self::Output> {
        // ONNX inference
    }
}

Model architectures:

Mamba-LOB - State Space Model (see README.md:295)
- Input: (batch, seq=100, features=40)
- Hidden: 128 dimensions, 4 Mamba blocks
- Output: (batch, horizons=3, classes=3)
- Parameters: ~500K
- Inference: <800ns
Decision Transformer - Offline RL
- Predicts optimal actions given past trajectory
- Context window: 20 timesteps
IQL - Implicit Q-Learning
- Value-based RL with expectile regression
- Used for market-making policy

Training

Models are trained in Python (see python/training/) and exported to ONNX:

import torch.onnx

model = MambaLOB(d_model=128, n_layers=4)
torch.onnx.export(model, dummy_input, "mamba.onnx")

Trained models stored in models/ directory.

Dependencies

nano-core - Core types
nano-lob - Feature extraction
ndarray - Tensor operations
ort (optional) - ONNX Runtime

nano-strategy

Location: crates/nano-strategy/ Description: Trading strategy implementations and RL environment.

Key Modules

MarketMakerStrategy (`market_maker.rs:1`)

Classic market-making with ML signals:

pub struct MarketMakerStrategy {
    config: MarketMakerConfig,
    position: i64,
    realized_pnl: f64,
    inventory_skew: f64,
}

impl MarketMakerStrategy {
    pub fn new(name: &str, instrument_id: u32, config: MarketMakerConfig) -> Self;
}

impl Strategy for MarketMakerStrategy {
    fn on_market_data(&mut self, book: &dyn OrderBook) -> Vec<Order> {
        let mid = book.mid_price();
        let spread = self.calculate_spread(book);
        let skew = self.inventory_skew * self.position as f64;
        
        vec![
            Order::limit(Side::Buy, mid - spread/2 - skew, qty),
            Order::limit(Side::Sell, mid + spread/2 - skew, qty),
        ]
    }
}

Configuration (market_maker.rs:15):

pub struct MarketMakerConfig {
    pub base_spread_ticks: u32,      // Minimum spread (default: 2 ticks)
    pub max_inventory: i64,          // Position limit
    pub order_size: u32,             // Contracts per side
    pub skew_factor: f64,            // Inventory penalty (0.0-1.0)
    pub use_ml_signal: bool,         // Enable ML-based adjustment
}

RL Environment (`rl_env.rs:1`)

Gym-style interface for reinforcement learning:

pub struct MarketMakingEnv {
    book: OrderBook,
    position: i64,
    cash: f64,
    timestep: usize,
}

impl MarketMakingEnv {
    pub fn step(&mut self, action: Action) -> (State, f64, bool);
    pub fn reset(&mut self) -> State;
    pub fn render(&self);
}

Action space:

Bid offset: {-5, -4, …, 0, …, +4, +5} ticks
Ask offset: {-5, -4, …, 0, …, +4, +5} ticks
Total: 11 × 11 = 121 discrete actions

Reward function:

r_t = ΔP&L - λ₁ * |position| - λ₂ * spread

Signal Strategies (`signals.rs:1`)

ML-driven directional trading:

pub struct SignalStrategy {
    model: Box<dyn ModelInference>,
    position_sizer: PositionSizer,
}

impl Strategy for SignalStrategy {
    fn on_market_data(&mut self, book: &dyn OrderBook) -> Vec<Order> {
        let features = LobFeatureExtractor::extract_all(book);
        let prediction = self.model.predict(&features)?;
        
        if prediction.confidence > 0.7 {
            vec![Order::market(prediction.side, self.position_sizer.size())]
        } else {
            vec![]
        }
    }
}

Dependencies

nano-core - Strategy trait
nano-lob - Order book access
nano-model - ML inference
rand - Action sampling

nano-backtest

Location: crates/nano-backtest/ Description: Event-driven backtesting engine with realistic latency and fill simulation.

Architecture

See detailed explanation in Architecture Overview.

Key Modules

BacktestEngine (`engine.rs:33`)

Core simulation loop:

pub struct BacktestEngine {
    config: BacktestConfig,
    event_queue: EventQueue,
    exchange: SimulatedExchange,
    latency: LatencySimulator,
    positions: PositionTracker,
    risk: RiskManager,
    metrics: BacktestMetrics,
}

impl BacktestEngine {
    pub fn run<S: Strategy>(&mut self, strategy: &mut S);
    pub fn results(&self) -> BacktestResults;
}

EventQueue (`events.rs:186`)

Priority queue implementation:

pub struct EventQueue {
    heap: BinaryHeap<Event>,
    sequence_counter: u64,
}

Event types (events.rs:10):

MarketData - Book update received
OrderSubmit - Order sent to exchange
OrderAck - Order acknowledged
OrderFill - Order executed
OrderCancel - Cancellation confirmed

LatencySimulator (`latency.rs:1`)

Models network and processing delays:

pub struct LatencySimulator {
    order_latency_ns: u64,
    market_data_latency_ns: u64,
    jitter_ns: u64,
}

impl LatencyModel for LatencySimulator {
    fn order_latency(&self) -> i64 {
        self.order_latency_ns + rand::gen_range(0..self.jitter_ns)
    }
}

SimulatedExchange (`execution.rs:1`)

Fill simulation with queue position model:

pub struct SimulatedExchange {
    active_orders: HashMap<OrderId, Order>,
    fill_model: QueuePositionModel,
}

impl SimulatedExchange {
    pub fn match_orders(&mut self, book: &OrderBook) -> Vec<Fill>;
}

Fill logic:

Limit orders matched only if price crosses
Queue position estimated from book depth
Fill probability: P = min(1, volume_traded / queue_position)
Adverse selection: Market orders get worse average price

PositionTracker (`position.rs:1`)

Tracks inventory and P&L:

pub struct PositionTracker {
    positions: HashMap<u32, i64>,
    avg_entry_prices: HashMap<u32, f64>,
    realized_pnl: f64,
}

impl PositionTracker {
    pub fn apply_fill(&mut self, instrument_id: u32, fill: &Fill);
    pub fn total_pnl(&self, current_prices: &HashMap<u32, Price>) -> f64;
}

RiskManager (`risk.rs:1`)

Enforces trading limits:

pub struct RiskManager {
    config: RiskConfig,
    peak_pnl: f64,
    daily_pnl_start: f64,
}

impl RiskManager {
    pub fn check_order(&self, order: &Order, position: i64) -> Result<()>;
    pub fn check_position(&self, position: i64) -> Result<()>;
    pub fn should_kill_switch(&self, pnl: f64) -> bool;
}

Dependencies

nano-core - Types and traits
nano-feed - Market data
nano-lob - Order books
nano-model - ML models
statrs - Statistical functions
rand - Random number generation

nano-gateway

Location: crates/nano-gateway/ Description: System entry point with REST API, metrics export, and configuration management.

Features

Axum web server - REST API for backtests and state queries
Server-Sent Events - Real-time streaming to web UI
Prometheus metrics - Time-series monitoring
Configuration - TOML-based system config

API Endpoints

Served at http://localhost:9090:

Endpoint	Method	Description
`/health`	GET	Health check
`/metrics`	GET	Prometheus metrics
`/api/state`	GET	Full engine state (JSON)
`/api/stream`	GET	SSE event stream
`/api/backtest`	POST	Run backtest

See Configuration documentation for API configuration details.

Binary Target

nanoarb (src/main.rs) Main executable:

# Run with default config
cargo run --release

# Run backtest
cargo run --release -- --backtest

# Custom config
cargo run --release -- --config custom.toml

Dependencies

All NanoARB crates
axum - Web framework
tokio - Async runtime
prometheus-client - Metrics
clap - CLI argument parsing
config / toml - Configuration

Build Configuration

The workspace Cargo.toml defines shared dependencies:

[workspace]
members = [
    "crates/nano-core",
    "crates/nano-feed",
    "crates/nano-lob",
    "crates/nano-model",
    "crates/nano-strategy",
    "crates/nano-backtest",
    "crates/nano-gateway",
]

[workspace.dependencies]
thiserror = "2.0"
anyhow = "1.0"
serde = { version = "1.0", features = ["derive"] }
tokio = { version = "1.41", features = ["full"] }
# ... more dependencies

Compilation Profiles

[profile.release]
opt-level = 3
lto = "thin"
codegen-units = 1

[profile.bench]
inherits = "release"

Testing Strategy

Each crate includes:

Unit tests - #[cfg(test)] modules in source files
Integration tests - tests/ directory
Benchmarks - benches/ with Criterion.rs
Property tests - proptest for randomized testing

# Run all tests
cargo test --workspace

# Run benchmarks
cargo bench --workspace

# Run tests for specific crate
cargo test -p nano-lob

Next Steps

Data Flow - Trace a tick through the system
Strategy Development - Build custom strategies
Backtesting Guide - Configure simulations

​Overview

​Dependency Graph

​nano-core

​Key Types

​Price (types/price.rs:1)

​Quantity (types/quantity.rs:1)

​Side (types/side.rs:1)

​Timestamp (types/timestamp.rs:1)

​Order (types/order.rs:1)

​Core Traits

​Strategy (traits.rs:48)

​OrderBook (traits.rs:6)

​ModelInference (traits.rs:160)

​Dependencies

​nano-feed

​Features

​Key Modules

​MdpParser (parser.rs:1)

​Synthetic Data Generator (synthetic.rs:1)

​Dependencies

​nano-lob

​Key Modules

​OrderBook (orderbook.rs:1)

​LobFeatureExtractor (features.rs:1)

​SnapshotRingBuffer (snapshot.rs:1)

​Dependencies

​nano-model

​Features

​Key Types

​SignalModel

​Training

​Dependencies

​nano-strategy

​Key Modules

​MarketMakerStrategy (market_maker.rs:1)

​RL Environment (rl_env.rs:1)

​Signal Strategies (signals.rs:1)

​Dependencies

​nano-backtest

​Architecture

​Key Modules

​BacktestEngine (engine.rs:33)

​EventQueue (events.rs:186)

​LatencySimulator (latency.rs:1)

​SimulatedExchange (execution.rs:1)

​PositionTracker (position.rs:1)

​RiskManager (risk.rs:1)

​Dependencies

​nano-gateway

​Features

​API Endpoints

​Binary Target

​Dependencies

​Build Configuration

​Compilation Profiles

​Testing Strategy

​Next Steps

Overview

Dependency Graph

nano-core

Key Types

Price (`types/price.rs:1`)

Quantity (`types/quantity.rs:1`)

Side (`types/side.rs:1`)

Timestamp (`types/timestamp.rs:1`)

Order (`types/order.rs:1`)

Core Traits

Strategy (`traits.rs:48`)

OrderBook (`traits.rs:6`)

ModelInference (`traits.rs:160`)

Dependencies

nano-feed

Features

Key Modules

MdpParser (`parser.rs:1`)

Synthetic Data Generator (`synthetic.rs:1`)

Dependencies

nano-lob

Key Modules

OrderBook (`orderbook.rs:1`)

LobFeatureExtractor (`features.rs:1`)

SnapshotRingBuffer (`snapshot.rs:1`)

Dependencies

nano-model

Features

Key Types

SignalModel

Training

Dependencies

nano-strategy

Key Modules

MarketMakerStrategy (`market_maker.rs:1`)

RL Environment (`rl_env.rs:1`)

Signal Strategies (`signals.rs:1`)

Dependencies

nano-backtest

Architecture

Key Modules

BacktestEngine (`engine.rs:33`)

EventQueue (`events.rs:186`)

LatencySimulator (`latency.rs:1`)

SimulatedExchange (`execution.rs:1`)

PositionTracker (`position.rs:1`)

RiskManager (`risk.rs:1`)

Dependencies

nano-gateway

Features

API Endpoints

Binary Target

Dependencies

Build Configuration

Compilation Profiles

Testing Strategy

Next Steps