ex-CTO and co-founder at ask_fm (DAU 15M+);
also: geek, software architect, mobile game developer, passionate machine learning/robotics engineer;
At ask_fm we had a huge experience moderating photo/video/text content. Managed to moderate around 3M+ images a day.
Had experience protecting our systems against spamers / hackers and frauders.
ask_fm was probably one of biggest system built with Ruby on Rails. Can finally answer the question - "Does Ruby scales?"
At ask_fm we did a huge work scaling system from just one server to ~800.
Database scalability. Application scalability. Network scalability. Statistics.