The web part of it is pretty easy to scale. You simply add more web servers. The problem is in the storage/db layer. I imagine the feed was the primary challeng

The web part of it is pretty easy to scale. You simply add more web servers. The problem is in the storage/db layer. I imagine the feed was the primary challenge scaling Twitter. Other components such as the search were probably also quite tricky. One thing i've never figured out is how Facebook handles search on your timeline. That a seriously complex problem. Linkedin Recently published a bunch of papers about their feed tech: https://engineering.linkedin.com/blog/2016/03/followfeed--linkedin-s-feed-made-faster-and-smarter https://engineering.linkedin.com/blog/2016/03/followfeed--li... And Stream's stackshare is also interesting: https://stackshare.io/stream/stream-and-go-news-feeds-for-over-300-million-end-users https://stackshare.io/stream/stream-and-go-news-feeds-for-ov...