Sitecore JSS component invoking a web api

Question

I had a react js application (http://localhost:3000) that invoked a web API (http://xyz) POST method. The way I accomplished that is - through the "proxy": "http://xyz" setting in the package.json of the http://localhost:3000 react js application. When I moved the react js application comp to Sitecore JSS, the call isn't successful - xhr.js:155

GET http://new-jss-app.dev.local/sitecore/service/notfound.aspx?item=%2fapilist%2fsignin&user=extranet%5cAnonymous&site=new-jss-app

Any pointers to help accomplish the call? Thanks.....