happy workaday Rust hacker here. Coming from higher level languages, the semantics make much more sense to me, after a quite harsh learning curve and some un-learning. Non lexical lifetimes is a game changer for rust learnability I think, and I more and more fail to see usecases where I can't just use it.
When dealing with cloud identity providers like AWS Cognito or Firebase and the likes, the option A is actually the most quick to implement. It's centralized for sure and not that fast, you are basically left with a JWT that acts as a session but you don't have to think about that much, it brings an ok level of security.
