Yeah, It's 100% about bot mitigation. I got hit pretty bad by some botnet a while back, saw 10-15 searches/second. Can't have nice things on the Internet I guess.

Don't really understand their motive either. Maybe they thought I was cloud hosted or used some expensive API to do searches and were attempting to rack up big bills or something.

:-|

I wish I had a good solution to this. Cloudflare to mitigate DDOS attacks has somewhat of a “baby with the bathwater” vibe (considering how much of a pain it is if you can't pass the CAPTCHA, or if you're on Tor), but I can't think of an alternative.

:-| indeed.

I've considered having a naked endpoint with a rate limiter that, when it hits some ceiling (dunno, sustained load of 2 RPS or so), offers the alternatives of going through an unlimited cloudflared domain, or waiting until the bots give up. But that might be annoying too.

You could try to push forward the frontier of accessible CAPTCHAs. You just need some tasks that basically all humans can do, but barely and bots can, that don't rely on vision, hearing, emotional response or cultural knowledge. Should be easy, right?