The interview, which consists of a resume drill and a live coding session, isn't inherently 'hard.' However, it requires a mastery of specific skills rarely practiced outside of HFT. Something I only fully realized after the interview was over.

HR call followed by 1 hour Technical interview followed by 2 1 hour technical interviews with trader / researchers. They were light on brainteasers and standard behavioural questions. Mostly they dived into my experience and projects I wrote about on my CV.