Citadel Securities Quantitative Trader interview experience

I had an introduction that led into technical questions with some brainteasers mixed in. One theme was estimation and rough guessing under uncertainty, alongside probability questions that were meant to feel quick and practical rather than deeply academic.

When I moved into the later stage, it was more intense and open-ended. I remember feeling like the final part asked for deeper reasoning than the earlier rounds, and the interview still had a learning-by-doing vibe. The overall difficulty trended upward across the process, and even with that, I stayed engaged because the problems were