Since it is built from the ground up around an event loop, asynchronous requests and responses as well as websockets work much more naturally. With Plack-based

Since it is built from the ground up around an event loop, asynchronous requests and responses as well as websockets work much more naturally. With Plack-based frameworks the PSGI spec is not built for asynchronous behavior, so you have to rely on hacks and use specific PSGI servers like Twiggy.