Comment by drum55

It’s not seconds though, it’s in the order of tens of milliseconds of work, it’s faster to complete the challenge than most http requests will take.

last difficulty 5 nonce 645376 in 9 ms (101.6MH/s, avx512-x16)

This takes many minutes to solve on a cellphone, 9 milliseconds on a cheap VPS. It’s not stopping anyone.