It would, apparently, replace Starman (the application server, the persistence layer and manager of processes). I have no experience at all with nginx Unit yet but nginx proper deserves mad respect, my only choice when I'm allowed to choose, so I have little doubt Unit will be wonderful if it isn't already. I've harped on it before but I'll say again uWSGI is far better than all the Perl alternatives for app servers. I have no idea how it stacks up against Unit today.