Backend

• Erlang
• FreeBSD
• Yaws, lighttpd
• PHP
• Custom patches to BEAM (BEAM is like Java’s JVM, but for Erlang)
• Custom XMPP
• Hosting may be in Softlayer

Frontend

• Seven client platforms: iPhone, Android, Blackberry, Nokia Symbian S60, Nokia S40, Windows Phone, ?
• SQLite

Hardware

• Standard user facing server:
  • Dual Westmere Hex-core (24 logical CPUs);
  • 100GB RAM, SSD;
  • Dual NIC (public user-facing network, private back-end/distribution);

Link