> but unless you do PoW (which is also ecologically a nightmare)

Can you expand? I don't see a problem with some napkin math. 5W load for 2 seconds is 0.002Wh (we have to let smartphones pass and not by doing PoW for 10s of seconds). 8 billion checks a day for a year = 8GWh.

I stand corrected. It's not a nightmare scenario (as for Bitcoins) - but I'm still of the idea that "useless" computations should be avoided (as we should avoid having 10MB websites).

In any case, according to some napkin math done by Kimi 2.6 (which by itself is probably already consuming more than all of my PoW challenges for the upcoming 5 years) - the situation looks incredibly in favor of PoW: https://www.kimi.com/share/19e7ef40-a432-8912-8000-0000b4a71...

Which makes me wonder why CloudFlare isn't switching to this already