We experimented with both tokio and async-std and picked tokio on the merits. This was ~2 years ago, so things may have changed a bit, but tokio provided a lot

We experimented with both tokio and async-std and picked tokio on the merits. This was ~2 years ago, so things may have changed a bit, but tokio provided a lot more out-of-the-box, and we also wanted a multi-threaded executor so its defaults worked well for us.