That, plus if I open dev tools and look at requests for even this site, the only things that small are three of the images (the orange Y in the corner, the vote arrow, and a 1x1 somewhere).

It wouldn't be possible to get that request rate outside of a microbenchmark, just because of the network speed the pi supports.

you can buy faster network cards for a RPi but this is missing the point: 100k req/sec is not a huge volume and a decent server should be able to handle it without issues.

it's not, people have been able to put >1G network cards on a Pi:

- 2.5G: https://www.jeffgeerling.com/blog/2020/testing-25-gbps-ether...

- 10G (in practice 3.6G max which is more than what most can expect from their ISP): https://www.hackster.io/news/10-gbps-ethernet-on-a-raspberry...