Generally it seems like async only has a real benefit when there are many connections.<p>Is there a scenario where using an HTTP client implemented with Rust's async features gives a substantive performance benefit?
That's correct. With many concurrent connections, you save memory (from thread stacks) and context swiches (since you don't need to switch thread to process each socket).<p>If all you want is a single request (and you have wait for results to continue work), you don't gain anything by going async.