When my stuff has been shared on HN and Reddit, I’ve seen peaks of around 500 rps (according to google analytics), so if you can hit 1k rps you’re almost certainly ready to weather any kind of viral sharing that a blog might experience. Several krps on cheap VPS hardware is easy with a good compiled language backend (Haskell’s Warp is a good one). If you use a node/python/ruby/other interpreted backend, you will need aggressive caching through a reverse proxy.