I would classify it more as a widget or add-on in that it's use lies in being added to an existing website (much like Google Analytics). The entire admin/dashboard area for managing sites, adding users, integrations etc is like a typical webapp though. The stack is a pretty vanilla LEMP stack on the backend, with some extra bits for handling queues. The trickiest piece is the widget that gets embedded on sites, it needs to be bullet proof across browsers and devices since it's used for feedback and testing. It needs to work on pretty much everything that people visit websites with.