Again, cryptocurrency would allow a proof-of-work mechanism but offload it so it needn't be real-time.
That is, do the proof-of-work before visiting the website, then present the currency token that proves the work has been done. The blockchain is there to prevent double spending of the currency token.
I do feel like this is a kind of "those who don't understand it are doomed to re-invent it" type of technologies.
No, I understand. I WANT it to be real time. I don’t want it to be offloaded.
You don’t need to worry about double spending or any of the privacy issues that come with a blockchain when the work is done real time. I know exactly how much work is being done on the server per request with this solution - one hash. There is no need to crawl through a block chain, or submit a transaction, or wait for an external system to catch up.
I want a solution to these crawling bots, not a distributed database. So why would I reach for a distributed database when this simple proof of work system works better, is more understandable, and doesn’t have external dependencies?
There's a sentiment here that I think is valid and I'm struggling to tease out the best version of it, along with providing a valid response.
I'll mention that, in an extreme case, one could provide a proof-of-work challenge that's directly tied to some cryptocurrency mining effort, so that the work/energy expenditure is captured by the one providing the challenge. This has the effect of the challenger giving money to the one providing the challenge, just in a real-time proof-of-work way. Since money is effectively being exchanged anyway, this punishes systems that don't allow up-front payments to do away with the page load delay.
That is, do the proof-of-work before visiting the website, then present the currency token that proves the work has been done. The blockchain is there to prevent double spending of the currency token.
I do feel like this is a kind of "those who don't understand it are doomed to re-invent it" type of technologies.