Design the infrastructure to serve a ChatGPT-scale assistant to hundreds of millions of weekly users.
The OpenAI capstone design. What separates passing answers: token-based capacity math, KV/prefix-aware routing instead of round-robin, and a degradation ladder for the day demand doubles overnight.
Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.
The OpenAI capstone design. What separates passing answers: token-based capacity math, KV/prefix-aware routing instead of round-robin, and a degradation ladder for the day demand doubles overnight.
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.
