Rust Crypto Exchange

This project is a high-performance cryptocurrency exchange built entirely in Rust. It features a modular architecture with separate components for the API, matching engine, WebSocket server, and database services.

Project Structure

The exchange is a monorepo containing the following crates:

• api: The public-facing RESTful API built with actix-web. It handles user requests, such as placing orders, checking balances, and getting market data.
• engine: The core matching engine of the exchange. It processes orders, matches trades, and maintains the order book for each market. It's designed for high performance and low latency.
• wss: A WebSocket server built with tokio-tungstentine that provides real-time data streams to clients. Users can subscribe to channels to receive live updates on trades, order book changes, and their own user data.
• db_filler: Fills the market data such as place new orders, updating orders, cancelling orders and adding trades by getting messages from engine. Uses tokio as the runtime.
• store: Handles all database interactions using sqlx with a PostgreSQL database. It's responsible for persisting trades, orders, and user data.
• common: A shared library containing common data structures, types, and utilities used across all other crates.

Getting Started

How to Run

1. Set up the environment:

   • Clone the repository.
   • Create a .env file in the root of the project and add the necessary environment variables for database connections, Redis URLs, and other configurations. You can use the .env.example file as a template. Or you can run cp .env.example .env for the default values.

2. Starting Services (via Docker):

   • Run docker run -e POSTGRES_PASSWORD=postgres -p 5432:5432 postgres to start a postgres database.
   • Run docker run -d -p 6379:6379 redis to start a redis server.

3. Run DB migrations:

   • First of all, you need to have a sqlx-cli installed to run the database migrations.
   • Navigate to the store directory cd store.
   • Now run migrations using the command sqlx migrate run

4. Run the exchange components:

   • Each component can be run separately. Open a new terminal for each service.
   • Engine: cargo run --bin engine
   • Database Filler: cargo run --bin db_filler
   • WebSocket Server: cargo run --bin wss
   • API Server: cargo run --bin api

Screencast

Screencast.from.2025-07-10.09-39-06.webm

Architecture

NOTE: Each orderbook runs individually on separate thread !

Order Placing :

• Initially client subscribes to the WSS server at channels like trade@SOL_USDC , depth@SOL_USDC. Then WSS subscribes to those channels on WSS_PUB_SUB.
• Then client sends a POST req to create an order to api
• api creates an order_id for the order. Then subscribes to that order_id on API_PUB_SUB and pushes the order to orders QUEUE.
• manager or the main core of the engine constantly get's order from orders QUEUE and sends the order to the correct orderbook.
• Orderbook validates and locks user funds. Then process against opposing orders and may sit on the orderbook if unfilled incase of limit order. Finally Settles the balance of makers and taker.
• Then Orderbook sends:
  • Order and Trade details to DB_Filler QUEUE,
  • Order Status and Filled Quantity of Order to API_PUB_SUB.
  • Trade and Depth details to WSS_PUB_SUB.
• api receives the order details from API_PUB_SUB and sends response to the client.
• DB_Filler then gets the trade and order details and updates to the DB
• WSS server gets updates about trade and depth details to the Subscribed Clients

API Endpoints

The following is a summary of the available API endpoints based on the code structure.

• GET /health: Checks the health of the API server.
• POST /order: Create a new order.
• DELETE /order: Cancel an existing order.
• GET /orders/open: Get all open orders for a user.
• POST /order/cancel_all: Cancel all open orders for a user.
• GET /depth: Get the order book depth for a market.
• GET /balance: Get the user's account balance.
• GET /trade/history: Get the trade history for a market.

WebSocket API

The WebSocket server provides real-time data streams. Connect to ws://127.0.0.1:8081 and subscribe to the following channels:

• Order Book: Get real-time updates on the order book for a specific market.
• Trades: Receive live trade updates for a market.

Note

• UserId's - random1, random2, random32 are set with initial balances for ease.

Pending Features

• OrderBook Recovery
• Testing

Contributing

Contributions are welcome! Please feel free to open an issue or submit a pull request 🙏.