I come from a Java background where the web application is always resident in the memory. This allows it to perform all initialization tasks at the startup itself and, unlike PHP, it does not have to do that again and again for every request.
I see a lot of options to run Django projects but not sure which one of them will allow me to achieve the above? Furthermore I already have a Nginx running at 80 so requests to Django needs to be routed via it.
Django is run by python, and has a process which stays loaded in the memory, much like java. Unlike php, Django will not reload all of its data per request, and it has an application scope. This is the reason why there are so many options for php hosting, but not as many for Django.
There are a few ways to use Nginx with Django, just google "nginx django" and you get a lot of results which teach you how, for example: https://code.djangoproject.com/wiki/DjangoAndNginx