[namjh]

> The problem is that in the ecosystem we are building the prevailing assumption is that anything async must also be Send, which means we end up using Send primitives even in non-Send contexts, which is always a waste.

Honestly I don't think every user want top notch throughput when writing asynchronous Rust applications. Most users would just want the correctness of the Rust type system, and its "lightweight" runtime characteristics compared to CPython, Node.js etc., which can provide fairly good performance.

The thing is, using Arc in single threaded runtime does not greatly harm performance. If it matters, you should be handling 1M+ rps per core and using multithreaded runtime because it scales better, which benefits from using threadsafe primitives.