I have a very straightforward metric for if something counts as “big data”: if it is possible, using consumer-grade data storage media, to fit all of the data inside of my mouth, then you should probably not call it “big data”.

At the present time (May 2024), you can purchase a 1TB MicroSD card from a variety of consumer retailers. The lower end of adult mouth volume is ~50 ml (and therefore, about 50 cubic centimeters), and a microSD card being 15x11x1mm, giving about a volume of about 0.165 cubic centimeters. So we reasonably fit 300 microSD cards in the typical human mouth: therefore, the “big data” limit is around 300 terabytes.

Regardless of how impressive having many millions of data points may seem in a vacuum - if I could fit your database in my mouth, I don’t think it gets to be big data any more.

(this would be tongue in cheek, if I didn’t have microSD cards in between my tongue and cheek)