I've never tried Rust or Rocket, but it appears to be gaining popularity, so I have the following questions for existing users: What's it like to work with? Do you prefer it to JS/PHP/Python for web related projects? Can you iterate on code quickly, or is there a compile step on every iteration? Are there stable libraries for interacting with MySQL/Redis/Postgres asynchronously? Is there good IDE support, for example…
Of the popular frameworks in languages you mention, Rocket is fairly close to Flask in terms of feel. Rust is a typed language and Rocket uses code generation and function's type signatures to automatically check the incoming parameters.
This can be fairly simple, like verifying+converting a param to a number. It can be fairly involved like setting it up so that if one of your handler function's arguments is an AdminUser, Rocket will take the user id from the request/cookie, connect to the database, and verify that the user is an admin. This is doable with middleware in many frameworks for the languages you mention but the difference is that this is on-demand based on the argument types.
> Can you iterate on code quickly, or is there a compile step on every iteration?
Rust is a compiled language. There's a compile step when you make a code change.
> Are there stable libraries for interacting with MySQL/Redis/Postgres asynchronously?
There are libraries for interacting with all those things. That said, the Rust async ecosystem is in a transition period at the moment. If you're familiar with the JS transition from callbacks to Promises to async/await, it's basically that. Check back in 6 months.
> Is there good IDE support, for example in Atom?
IDE support in Rust isn't particularly good yet. In general, find references and go to defintion work but autocomplete does not.