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Part 2: Product Data Models – Ethereum Payment

In this series of articles, I’m doing a walkthrough of a hobby project I’ve worked on, a payment system for the Ethereum blockchain. Go read the intro article for more context about this project.

In this part, I will cover the following topics:

  • Product details, whitelistings, coupon codes
  • Displaying purchases and subscriptions, products available, and past purchases
  • Data models for products and whitelistings

None of what is described in this article is about web3, it’s all really web2 development. However, I do have to describe it to lay the foundation for parts 3 and 4 that will be focused on interacting with the blockchain, and with a recap of what I’ve learned about what crypto wallets and blockchain for developing mass-consumer product experiences.

Below are the data models used for products, purchases, and whitelistings and coupons (click to enlarge).

The data schemas used to represent products, purchases, and whitelists/coupons (click to zoom)

The follow diagram shows three user flows: the first flow shows products for non-signed in users, the second flow for signed in users, and a third flow just to display the current status of the access rights.

System diagram showing three user flows to display available products, past purchases, and current access rights.

Part 1: Authentication and Crypto Wallet Management – Ethereum Payment

In this series of articles, I’m doing a walkthrough of a hobby project I’ve worked on, a payment system for the Ethereum blockchain. Go read the intro article for more context about this project.

In this part, I will cover the following topics:

  • Connecting a crypto wallet via a frontend, and detecting states in MetaMask
  • Backend endpoints needed to manage wallet connections, wallet signature, and JSON Web Tokens.
  • Data models for users.

You will find that there isn’t much complexity in this article. Authenticating a crypto wallet is most about calling methods from the wallet API from the frontend, and then passing data around between the frontend and the backend for verification.

Connecting a Crypto Wallet

Whatever software you build that will have to interact with the Ethereum blockchain, either reading data or transacting, you’ll need to connect to an Ethereum node to access the Ethereum blockchain.

For most use cases, you won’t be running your own Ethereum node, and you won’t be calling directly any Ethereum node either. Instead you’ll use a third party that offers a centralized point of access to the blockchain: you connect to their backend servers, which are connected to the blockchain. It’s kind of counter-intuitive that we have to use centralized third party providers when you think about it given that one of the core tenets of the blockchain is that it’s fully decentralized, but that’s what we have to deal with these days.

As a human user of the blockchain, you need a crypto wallet to initiate various actions and execute smart contracts. Every Ethereum client implements the same JSON-RPC specifications, which is the standard that applications can rely on to interact with the blockchain.