It isn’t mentioned in Netlify’s list of supported languages for cloud functions (JS, TS, and Golang), but you can write cloud functions in Rust and deploy them on Netlify’s free plan. I tried it last night with warp_lamda and it worked.
I’ve been looking for ways to deploy free cloud functions that don’t require a credit card. My biggest worry with Firebase and AWS Lamba is that there isn’t a way to cap the billing. With services that don’t let you cap billing, it’s possible to experience bugs that cost thousands of dollars. I think it’s too much of a risk for casual projects. I’d rather have the functions automatically shut off when a certain billing limit is reached (like $5/month). Without a way to cap billing, $5/month on DigitalOcean has been a safer bet than “free” on Firebase.
I haven’t tried it yet, but there is another database called FaunaDB that doesn’t seem to have the billing risks of Firebase and AWS. I’m hoping to try it soon.