DPO vs RLHF: 5 Interview Questions That Trip Up Developers

#dpo #rlhf #llmfinetuning #interviewquestions

The Question That Stumped 80% of Candidates

"Walk me through how DPO eliminates the reward model." Simple enough, right? I've sat through dozens of LLM interviews where candidates confidently explain that Direct Preference Optimization (DPO) is "simpler than RLHF" — then completely blank when asked to derive why. The math isn't even that hard. The problem is that most tutorials hand you the final loss function without showing the sleight of hand that makes it work.

Here's what actually trips people up: DPO doesn't eliminate the reward model. It implicitly defines one. And that distinction matters when your interviewer asks follow-up questions.