Hi @gabotechs ,
The approach of using short lived pre-signed URL is genius!
I was looking to solve the same problem - how to use serverless functions and stream results.
I was thinking of building a cloud service that would do that. Although the developer experience and security would be no as great as yours, as you would have to expose the API key of the cloud service to the frontend. I built a landing page for it, but didn't get enough traction and abandoned the idea.
That said, I recently released a library for processing streamed JSON on the frontend.
Anyway, very well done!
And, by the way, the waiting list on your website seems broken. It shows me a 404. after I fill it in.