This is quite a fun website, what have you used for the backend, i've been wanting to get more deployments for small web tools but the hug of death always worries me

I'm unsing Laravel. I think any framework you are familiar with will do. I'm using frameworks even for single page application, cuz you never know how it turned.

I think the danger of "hug of death" is overblown. Hardware gets more powerful over time, and bandwidth expands. I had a project with about 60k unique users per day, and that traffic lasted for several weeks. I didn't take any special measures, although I was prepared to switch to a more powerful server.

I'd be worried about what to do to get to 60k users. :)