Obviously, "slow" has very different meanings depending on context. Allocating a task object or interacting with the runtime in any way may be quite slow when y

Obviously, "slow" has very different meanings depending on context. Allocating a task object or interacting with the runtime in any way may be quite slow when you're in a tight inner loop, but it may be perfectly fast in the context of handling an HTTP request. Async is almost never free of charge. The only language that can get close to zero cost is Rust, but even it needs heap allocations for async recursion.