Inventory Management system

Overview

Your task is to build a backend service that simulates an inventory management system for a company providing cross-border liquidity services. The company operates liquidity pools in multiple currencies and manages currency transfers for users sending funds between different currencies.

The system will support the following currencies:

• USD, EUR, JPY, GBP, and AUD.

Objective

The key objectives are to create a system that:

• Manages liquidity pools across various currencies.
• Tracks inventory, revenue, and FX rates for each transaction.
• Dynamically rebalances liquidity pools based on transaction data to maintain optimal balances.

Language and Framework:

• Preferred: Node.js with TypeScript.
• Alternative: Any language or framework of your choice is accepted.

Requirements

1. API Endpoints

   • Transfer Request: POST /transfer

     • Accepts a transfer request from a sender to a receiver, converting currency X to currency Y.
     • Uses the FX rate to calculate the amount in currency Y and apply a transaction margin.
     • Immediately debits the amount in Y from the liquidity pool and records it.
     • Adds revenue based on the applied margin.
     • Takes into account currency-specific settlement times.
       • Note: In the real world, settlement times typically depend on the country and payment rails. For this exercise, however, we’ll simplify by making settlement times dependent on the currency instead.

   • FX Rate Update: POST /fx-rate

     • Receives mock FX rates between supported currencies.
     • Updates the stored FX rates for use in transfer calculations.
     • The mock script, mockFxRateSender.js, should be used to send rate updates to this endpoint every 3-5 seconds.
       • Example payload from the script:

         {"pair":"AUD/JPY","rate":"82.6666","timestamp":"2024-11-11T11:22:18.123Z"}
         

     • The script will occasionally send extreme fluctuations (5% chance of a 5-10% change) to simulate market volatility.

2. Liquidity pool rebalancing

   • Periodically rebalance liquidity between pools to maintain optimal balances.
   • Takes into account transaction volume and send/receive imbalances.
   • Ensures each pool is adequately funded to meet anticipated demand.
   • Track available liquidity in each currency pool in real-time.

3. Revenue Calculation

   • Track revenue by calculating the margin on each transaction.

4. Foreign Exchange Rates

   • Store FX rates and allow historical lookups for use in transfer and revenue calculations.

5. Data Persistence

   • Use reliable data storage to maintain inventory levels, transactions, FX rates, and revenue.
   • Ensure atomicity and resilience to outages for each transaction.

6. Additional Requirements:

   • Use configuration files or environment variables for adjustable parameters, such as margin percentages, currency settlement times, and rebalance frequencies.
   • Ensure logging and error handling, especially for scenarios with missing liquidity or FX rates.

Initial Balances per Currency

• USD: 1,000,000
• EUR: 921,658
• JPY: 109,890,110
• GBP: 750,000
• AUD: 1,349,528

Currency Settlement Times

Each currency has a predefined settlement time, simulating the delay for funds to be confirmed in liquidity pools. These settlement times are specified in seconds for easy testing:

• USD: 3 seconds
• EUR: 2 seconds
• JPY: 3 seconds
• GBP: 2 seconds
• AUD: 3 seconds

Requirements

For development, you will only need Node.js and a node global package manager, Yarn, installed in your environement.

Node

• Node installation on Windows

  Just go on official Node.js website and download the installer. Also, be sure to have git available in your PATH, npm might need it (You can find git here).

• Node installation on Ubuntu

  You can install nodejs and npm easily with apt install, just run the following commands.

  $ sudo apt install nodejs
  $ sudo apt install npm
  

• Other Operating Systems

  You can find more information about the installation on the official Node.js website and the official NPM website.

If the installation was successful, you should be able to run the following command.

$ node --version
v16.17.0

$ npm --version
8.15.0

If you need to update npm, you can make it using npm!After running the following command, just open again the command line.

$ npm install npm -g

Yarn installation

After installing node, this project will need yarn too, so just run the following command.

  $ npm install -g yarn

---

Install

$ git clone https://github.com/Timoolz/sphere-take-home.git
$ cd sphere-take-home
$ yarn 

Configure app

Open sphere-take-home/.env then edit it with your settings. You will need:

A sample.env file has been provided

Running the project

Run the following commands

$ yarn start:dev

Running the Unit Tests

Run the following commands

$ yarn test