Recruiter outreach (email), led to a call with the recruiter, and then a technical screen (Skype, coding in an online editor) with an engineer, which in turn lead to an onsite. The onsite was very long, and had me talking to about 7 different team members (mostly engineers, and one interview with a designer for cultural fit); it lasted the entire day. Lots of tree questions (implement a BST, score sudden-death tournament results with a minimal binary tree data structure, encode an alien dictionary using a tree and then produce a dictionary using topological traversal), and a "rebuild Twitter from the ground up" scaling/architecture question.