This isn't any normal introversion, this is advanced introversion.
There are situations where you wanna run through the store quickly without "stupid questions".
Sometimes I snap at clerks who are being too persistent (in a bad way) and play mind games asking ridiculous questions or doing impossible to compleete requests. That is usually at shops, where you often have opportunity for a small talk. For loose example in draft beer shop the clerk being too insistent on buying nuts, while me visited the shop after hardware store where I bought some fasteners, nuts included and I reply "no, in fact I've already bought nuts for the beer" and demonstrate the nuts, clearly showing that I'm gonna eat fasteners them with beers. Annoying clerks often shut up and leave me alone with confused face. If they persuade me on the first try - I leave them alone, along with bought proposed stuff.
For Christmas a few years ago, one of my parents got me a shirt that says "You read my shirt. That's enough social interaction for today." (They often get me the stuff they think is funny because I wear shirts with words on it, and they don't. Somehow, I'm "the snarky one".) In actuality, all it does is get the cashiers to comment on how much they like my shirt, which, since I often just grab the one at the top of the pile, I've generally forgotten which one I'm wearing.
