Prefill vs decode, why are the two phases bottlenecked differently, and why disaggregate them?
One forward pass, two opposite performance regimes. The arithmetic-intensity argument that explains TTFT vs TPOT, GPU pool design, and why the big serving stacks split the phases onto different hardware.
Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.
One forward pass, two opposite performance regimes. The arithmetic-intensity argument that explains TTFT vs TPOT, GPU pool design, and why the big serving stacks split the phases onto different hardware.
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.
