Design a doc-QA system for a healthcare customer that reliably says 'I don't know' instead of guessing.
In high-stakes domains a wrong answer is worse than no answer, but a system that always abstains is useless. The selective-prediction design, the layered abstention triggers, and the two metrics that govern the tradeoff.
Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.
In high-stakes domains a wrong answer is worse than no answer, but a system that always abstains is useless. The selective-prediction design, the layered abstention triggers, and the two metrics that govern the tradeoff.
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.
