I was investigating uses of unsafeToInlineFuture in the code, and found that in AsyncWorkScheduler::_targetHostAsync, it looks like the intention is to run the continuation on an executor thread:

            return targeter->findHost(readPref, CancellationToken::uncancelable())
                .thenRunOn(_executor)
                .unsafeToInlineFuture()
                .then([shard = std::move(shard)](HostAndPort host) mutable -> HostAndShard {
                    return {std::move(host), std::move(shard)};
                });

However, based on recent discussion (linked in comments), .thenRunOn(...).unsafeToInlineFuture(...) will actually just run the continuation inline, not on the executor provided in thenRunOn.

This might not be a big deal in this function (if so, feel free to close as Won't Fix), but I wanted to raise it as it looks like the intended behavior doesn't match the actual behavior here.