This project was handed to me as my first agency assignment. The base functionality had already been built, but the client needed some updates to be made. I've been iterating on the backend and frontend of this app for many months now, though it's only in short bursts (usually between challenge cycles).
The site uses MySQL, Express, React, and Node (MERN stack), so I've had some really good experience updating the database models, querying for certain data, updating the Express API, all in addition to extensive React development.
This app has been used by tens of thousands of unique visitors, and functions as a significant marketing tool for 1Up Nutrition. The components use Material UI for base styling, and state management is accomplished using Redux.
If you'd like to see the app in all its glory, check it out here (but you'll need to create an account to do so).