Mastodon Clone by Red Planet Labs
Summary:
Rebuilt the Mastodon backend from scratch and made it able to handle Twitter-scale (500M users, 20M writes/second, unbalanced social graph, etc.). Thus implementation is only 10k lines of code and is also significantly simpler than the existing Mastodon implementation. This clone is running at mastodon.redplanetlabs.com.
Full Article : Read here
this sounds amazing, it looks like they even made it possible to search statuses or posts if I understand it correctly.