X Software Engineer interview questions

HackerRank test (unlimited time with a recommended max of 90 minutes, which I exceeded by a few minutes), phone interview, followed by a three onsite interviews (two technical, one culture fit). All interviews, with the exception of the HR test are conducted by the team you'd be working on if given an offer. There was a 3-4 month period between my original application (and HR test) and the follow up. The phone and onsite interviews were scheduled in quick succession, very well coordinated. Everyone I intereacted with strived to make me feel welcome and at ease.

After speaking with a Twitter recruiter and an introductory call, did two screening calls and an onsite, with about a week between each phase. The first call was high-level experience based, but also spent some time describing the team structure. The second call was more technical, and included a screen-shared coding problem. The onsite was broken into four one hour parts with a break for lunch. Each part was conducted by two engineers. Three parts focused on white-boarded coding problems with an algorithms/data structures focus, while one was more soft-skills and experience focused (name a contribution you made to a team you were proud of, name a mistake you made at a previous job and steps you took to fix it, et cetera). All parts had a ten minute section for questions from the candidate.