Of course, now that increasingly more work is being done on the client side, or by communicating with microservices, Rust makes more sense for a pure API backend. There's a lot less ecosystem needed there; mostly just bindings to whatever database you need to talk to, possibly some other stuff.

So if you're just going to be exposing a RESTful API backend for a JavaScript based frontend, or even for a Rails app frontend to talk to, Rust makes a lot more sense.

Also, the only way an ecosystem gets bootstrapped up is by people scratching their own itches. By starting to write web services in Rust now, and implementing those things that aren't yet implemented, you can help to bootstrap it up. Of course, that only works if you have the extra time to spare to do so, but for those things that only need one or two extra things that don't yet exist, it may pay off due to the lower chances of having to debug runtime errors, less time and complexity spent trying to make it scale out, etc.