I was initially contacted for a phone screen, which went well enough. However, the interviewer wasn't super responsive, so I didn't have such a great feeling about it.

A few days later, I was invited to schedule an on-site interview, and the process went amazingly from there.

The questions asked on-site were interesting and challenging. Everyone I talked to was incredibly smart and offered insightful advice. The recruiters were also really responsive.

Although I received a rejection just a few days later, I came away with an appreciation for all that Jane Street stands for and an overall very positive experience.

It wasn't required to use a functional programming language, but it definitely would have helped for some questions.