
“Get up and running quickly with Express.js and the Shopify API.”
This project, Shopify Express, has been deprecated by Shopify, and the company will no longer be maintaining it. They suggest exploring their other libraries such as @shopify/koa-shopify-auth, @shopify/koa-shopify-graphql-proxy, and shopify_app if you are interested in building a Shopify app using first-party tools.
Shopify Express is a deprecated project by Shopify for building Express.js apps that consume the Shopify API. It provides features like mountable routes for authentication and API proxying, shop session storage, and customizable strategies for storing persistent data. While Shopify will not be maintaining this project, developers can still fork the codebase and continue using it if desired.

Express.js is a simple Node.js framework for single, multi-page, and hybrid web applications.
Shopify offers headless commerce capabilities through its Storefront API, allowing developers to use their own front-end technology to create custom storefronts or sales channels while using Shopify as a back-end system