Get and Post request 404 error

This is because you are running a React SPA. The solution to this issue is outlined in the following support guide as well as in this Netlify documentation and this Create React App documentation.

With the database

I suspect you have a proxy set up (e.g. in the package.json) which allows this to work. You have two choices on Netlify:

  • call the server URL directly from within the app; or
  • create a proxy to the database server to use relative paths (e.g. /data.)

Documentation for the latter you will find Proxy to another service.