So one of the articles I read said it happens through conversation and asking prodding questions about last names, your diet, etc. And then, after getting enough info, the higher caste person will start shitting on the lower caste by not inviting them out, telling everyone else about the lower castes person’s “status” etc.
Edit: It even goes as far as only seeing higher caste folks gaining positions in IT and stuff. I’ll see if I can find the article later.