Design a multi-model router or cascade that cuts cost without dropping below a quality floor.
Sending every request to the frontier model is the lazy bill. The patterns that route by difficulty, the verifier that enforces a hard quality floor, and the failure mode that turns a cost-saving cascade into a worse, slower system.
Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.
Sending every request to the frontier model is the lazy bill. The patterns that route by difficulty, the verifier that enforces a hard quality floor, and the failure mode that turns a cost-saving cascade into a worse, slower system.
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.
