Developing for potential high traffic website (Startup) which will be kind of like a news website ( Heavy on reading). One of the ways user will interact will be through comments. Thus a social login comment, and threaded comment is in consideration.
Question
Will offloading the login/comment/analytics to third party like disqus/livefyre/ intense debate etc will have any positive impact in sense that more concurrent users can be handled by the server. i.e. will having logged in users vs having NO logged in users will have better performance. e.g. Full page Static caching can be potentially used if you have no comments/login as Javascript will will be used for both login/comment and analytics
Note: This maybe not expression engine specific, even then what is opinion for handling high traffic with good efficiency for read heavy site.
Edited for simplicity.