Design the training infrastructure for RLHF/PPO. Why are there four model copies and how do you fit them?
RLHF with PPO is not one model training, it is four models in the loop at once, three of them on the GPU during every step. The memory math and the generation bottleneck are what catch people out.
Updated Sep 2026 · Grounded in real GenAI, LLM, and AI/ML engineering interview loops and written to a senior-engineer editorial bar.
RLHF with PPO is not one model training, it is four models in the loop at once, three of them on the GPU during every step. The memory math and the generation bottleneck are what catch people out.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
