Two interviews, both with technical interviewers. The second interview was with the engineering manager for the team.
Initial screen with technical questions: difference between a process and a thread. Implementing basic linked list algorithms.
Second interview went about double the allotted time. Grilling on the resume, plus some basic questions on bit shifting in C. Resume questions were significantly deeper and more challenging than the coding section. Exploring limits of candidates knowledge on projects they're familiar with.