When you say “running on my discourse app”, do yo mean in the server container or in the client browser? The discourse app consist of frontend code running in browser and backend code running in server.
Since you sad “ajax to” I’m under the impression that your code is running in browser. As mentioned earlier, the best way is to test and see if it is OK.
If you code is running on server side, it should be OK as long as your external nginx is configured correctly.