⚠️ Warning: Do not use a real password for your wallet.

Introduction

I built a crypto Venmo-like app as part of a backend challange with the following features:

• Users can log in with various social accounts or a wallet.
• On account creation, an embedded wallet is encrypted with a user-defined password and stored securely.
• Users can send money, sign a message, & check their balance.
• Works on the Sepolia Network

The app uses an AWS Serverless TypeScript backend and a Next.js frontend deployed on Vercel. My focus was to build a functional, production-ready product within a few days, showcasing:

• CI/CD pipelines
• Ethers.js for wallet creation and Ethereum interaction
• Unit testing with JEST
• Encryption and security best practices
• TypeScript, TypeORM, Zod, and Middy
• Serverless framework with AWS
• DB migrations using TypeORM-cli

Deployed at: https://vencura.sparakis.com

Cheers,

Konstantinos Sparakis

How to Run Locally

1. Clone git repo locally
2. Get a copy of the .env file from @Ksparaks, or fill out your own variables into the backend .env
3. Inside the backend folder, run migrations if using your own database:

   npm run migrate:up

4. Run Backend locally: open a terminal, navigate to the backend folder, and do the following:

   open serverless.yaml and comment out the -serverless-better-credentials-plugin
   npm i
   npm run dev

5. Run Frontend: open a terminal, navigate to the frontend folder, and run:

   npm i
   npm run dev

6. go to localhost:3000

TODO's & Proggress

10/10/24 - The app is now fully functional and I am turning my attention to testing, cleaning & organizing the code as well as getting CI/CD Pipelines

Things on my list to improve

Backend

• Get backend deployed automatically with github action
• Add Jest tests and coverage of Backend
• Ensure Backend Typescript passes Eslint
• Encrypt SQS message since it contains a password
• Ensure there is no logging of passwords
• Get Zod body/path/query validation built into the middleware chain.
• Add better check for wrong password input
• Update IAM role to be of least privelage
• Update cors origin to restrict cors.

Frontend

• Clean up Code Organization
• Need loaders while frontend is calling backend
• Buttons need to be debounced on api actions
• Ensure password clears out on logout
• Rework UI

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Backend Excersize Original Prompt

In this exercise, you are going to build the Venmo of wallets. 💰  We call it “VenCura”

🤯 Thank you GPT ❤️ “The name combines the words "Venmo" and "Custodian" to create a unique name that suggests a safe and reliable financial service. "Cura" means "care" or "guardianship" in Latin, which fits with the idea of a custodian service.”

In this take-home, you will build an API platform (with a basic UI) to generate custodial wallets on the backend with support for basic actions. We leave it kinda open-ended to not limit your creativity and to let you focus on things that you are interested in, within this problem.

Requirements:

• An authenticated user can create at least one account/wallet.
• All the interactions with the custodial wallet would be done on the backend via an API.
• A user can perform at least these actions on the wallet:
  • getBalance() → balance: number (get the current balance on the wallet.
  • signMessage(msg: string) → signedMessage: string (The signed message with the private key)
  • sendTransaction(to: string, amount: number) → transactionHash: string (sends a transaction on the blockchain)
• Basic UI to interact with the API.
• We encourage you to use the language/framework that you’re most comfortable with as long as it is a language we are familiar with (Javascript/Typescript, Ruby, Python, Java, and Scala). Internally, we use TypeScript, Node and React, but our core product needs to work seamlessly with many different build tools and frameworks.

What to focus on:

• Code + API + Schema design and implementation.
• Security considerations (could be in a writeup).
• Testing.

UI:

The main focus of this takehome is the API/Backend experience. The UI should allow you to showcase the functionality that you built on the backend.

Tips (you don’t have to follow any of them):

• You can use any open source library for managing the wallet interactions on the backend
  • Ethers has a Wallet class that handles the private key and common methods
• You can use these faucets to get some free sepolia (assuming that you are building it on Ethereum)
• Here are two RPC infura end-points for ETH testnets that you can use:
  • Seopolia - https://sepolia.infura.io/v3/91de7ed3c17344cc95f8ea31bf6b3adf