Facebook is very efficient in hiring. The HR department first sent some regular questions for me to answer, including my availability to start working and so on. They then arranged the phone interview directly.

On the same day as my phone interview, they arranged for on-site interviews. I was impressed with how efficient they are.

The interview questions were not extremely difficult, but I can tell they want people who understand the most basic concepts really well and can code clean and bug-free at once or after a few hints. The design questions were challenging, though. Be prepared for that.

The interview questions included Two Sum, Reverse Integer, Edit Distance, Clone Graph, etc.