Twitter uses what they call top grading, but really isn't, it's just a 1 hour reverse chronological set of questions through the most relevant/recent of your work history, asking the same set of defined questions for each role you had. Really just a structured way to understand your history in a consistent way. It basically the same as asking someone about their work history, but in a structured way.

  It is absolutely definitely not the actual top grading of multi hours of interviews , phoning references etc.