Do you still need a backend for fast prototypes?

I want to share with this:
https://www.youtube.com/watch?v=TSDyxtVbbME

What do you think indiehackers?:) anyone use actualy or used before?

Today i'm finish two days hackaton (hackyeah2020)... we spent some hours to provide backend / auth..

I started thinking about fast protypes - then I watch this video.