https://github.com/GSG-G11/shoestore/blob/b9c46b5d4bfb9942f1492a135274736bf9370723/server/controller/getProductID.js#L5

in responses you send the 
1.   .json({ status: 201, message: 'Product Added', product: rows[0] }))
2.  .json({ status: 200, message: 'Product Deleted' }))
3. .json(rows))
4. .json({ status: 200, message: 'Product Updated', product: rows[0] }))

should be consistent when we send a response for client side, moreover why you send a status in the body of response if we have it in status > res.status(200)

here is a question for you all, what if the rowCount equal 0, I mean what if there is no products in data base? In the same context we handle the 4xx errors in catch of promise, not the internal server error, we handle this error in Express error middleware like this ;

const serverError = (err, req, res, next) => {
  return res.status(500).json({ message: 'internal server error 500' });
};

you did a good work, all issues just to be a professional developers ;)

https://github.com/GSG-G11/shoestore/blob/b9c46b5d4bfb9942f1492a135274736bf9370723/server/database/config/connection.js#L8

For many reason Switch is better than If-else in this situation. I advice you all to read this essay, Explained everything. https://www.geeksforgeeks.org/switch-vs-else/

https://github.com/GSG-G11/shoestore/blob/b9c46b5d4bfb9942f1492a135274736bf9370723/server/database/build/build.js#L9

If you have an error in this Promise, you will see this message " UnhandledPromiseRejection" which means you are dealing with async code, that promise is rejected but you don't handle the Rejection. I suppose you forget add.catchhere, and you should do it to know where is the error happened

https://github.com/GSG-G11/shoestore/blob/b9c46b5d4bfb9942f1492a135274736bf9370723/client/src/App.jsx#L40

Avoid console.log and commented Lines in your codes, you missed handle the login state, your users can add to cart without login. and the login button didn't work !

some issue i saw it in your code...

  componentDidMount() {
    const { id, buttons , changeCart} = this.props;
    if(typeof buttons === 'string'){
    const products = JSON.parse(localStorage.getItem('products'));
    const addedToCart = products.some(item => item.id === id);
    this.setState({ addedToCart });
    changeCart(products.length)

  }

why we use component did mount here? I advice you to read this essay about local storage and what is the max size we can store in Local storage, should pass this data from parent component is better than this way. we can pass all data we need as props,

componentDidMount we use it when we have a http request in this component.

In contrast you did a great work and applied the concept of State and how we handle it very good, moreover you separate your components VERY GOOD.

GREAT WORK.