We do not yet have a Rust SDK, so you will have two options on how you can use SuperTokens:
1) Query the SuperTokens core via your Rust backend via http API calls. This way, you can make your own sign in / sign up etc routes which the frontend can call, and in turn these routes will call the core. The API spec for the core is:
https://app.swaggerhub.com/apis/supertokens/CDI.
2) Spin up an auth server in nodejs, python or Golang and use our backend SDK in them. The frontend would query these processes for auth related operations and in turn would receive a JWT which you can sent to your Rust backend. Your Tust backend would in turn [verify the JWT](
https://supertokens.com/docs/session/common-customizations/sessions/with-jwt/jwt-verification) and create it's own session to talk to the frontend.
I would recommend the (2) approach as it's lesser work.