I'm not one of their employees and yet I know how their build system works, how they store more photos than the rest of the internet combined (Haystack), how they process their analytics and likes (HBase counters + scribe + ptail + puma), how they store messages (HBase), how their data centers are built (open compute), the list just goes on and on.

As far as large internet companies goes Facebook has one of the most open engineering departments I've ever seen.