Rigorous but fairly reasonable in my experience. The technical problems often has a twist but if you have strong fundamentals you should be able to perform well. The recruiter and interviewers I interacted with are all very nice people.
J'ai passé un entretien chez SpaceX (Hawthorne, CA)
Entretien
4 rounds, 1 with technical recruiter, 1 with engineer, 1 with manager, and onsite. first 3 are over the phone. onsite was the challenge, consists of presentation, one-on-ones, and tour.
30 min call on personal projects and technical questions with recruiter. Technical questions were relatively simple and focused on engineering fundamentals, about cantilever beam, incompressible/compressible flow, and ideal gas questions.
Questions d'entretien [1]
Question 1
How does flow velocity of an incompressible fluid that is in a pipe change when there is a constriction in the pipe?