The most-reported decomposition prompt in the FDE canon. Almost every candidate builds a routing model, and almost every candidate is optimizing the wrong term of the equation.
Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.
The most-reported decomposition prompt in the FDE canon. Almost every candidate builds a routing model, and almost every candidate is optimizing the wrong term of the equation.
The tell we score on is whether you decompose the response-time interval before you decompose the system. Candidates who go straight to routing have skipped the only step that would have told them routing is usually the smallest movable term. The second tell is the metric: propose the mean and you have quietly designed a system that makes the worst-served neighborhoods worse, and a good interviewer will let you finish before pointing that out.
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