I used Django + nginx + uWSGI to deploy a website to example.com (this is also the hostname of my instance where I put the Django app on Google Cloud Platform) following the instructions here https://uwsgi-docs.readthedocs.io/en/latest/WSGIquickstart.html.
Now here's the strange thing. I found that all devices under my university's WiFi can access my website (http://example.com) but devices outside my network (for example, in another city) cannot access it. Does anyone know what is going on here? Thank you very much in advance.
Found out where the problem was with the help of my friend.
Turned out I pointed my DNS to two ip addresses and this caused the problem. When people at other places visit my website, they were directed to the other ip which only showed them the nginx welcome page.
Learned a useful command 'ping www.example.com', this helps you identify the ip address associated with www.example.com