Great talk! One thing that would have been nice to call out for n00bs like myself is how in SOP Futures can't cancelled. I knew that .await took ownership of the future so that drop() could not be called on it, so given how futures are lazy, it wasn't clear to me how to cancel a future after .await had been called. I later researched how select! and Abortable() did this, but could be nice to include a callout in the beginning of your talk if you ever do it again. Otherwise, nice work!