Medusa

Medusa is an open-source commerce backend for teams building a storefront that does not fit a hosted platform's model. The core is a modular Node.js server that exposes commerce primitives - products, carts, orders, customers, regions - through an API. The architecture is the differentiator. Commerce capabilities are modules with defined boundaries, so a team can replace the default implementation of one area without forking the whole system. A custom pricing module or a custom fulfillment integration plugs into the same interfaces the defaults use. Medusa is headless: it provides the backend and the API, and the storefront is a separate application. The project publishes a starter storefront alongside the server, but the server does not assume a particular front end. That separation is what lets a team use it with a custom storefront, a mobile app, or a marketplace model.