First, I completed an online assessment which had two easy-medium questions. A few weeks later, I received an email to schedule two phone interviews.

The interviews went well, and the next day the recruiter asked me to set up one additional phone interview as they needed some more data points. Two weeks later, I had my third interview.

It also went well. Overall, none of the three interviews went poorly; I'm pretty sure I aced two of them.

A few days later, I received an email from the recruiter stating I was rejected, with no reason mentioned. I feel the bar is very high for grad students.

One question in each round, with follow-ups. All were on the difficult / LeetCode hard level.