Specify Proximity-Based Request Routing

Design proximity-based request routing. Explain what information a request and a destination must provide, how proximity is measured, and how the routing decision should account for unavailable or unsuitable destinations. ### Constraints Only the proximity-routing objective is supplied. The distance metric, destination eligibility, capacity, tie rule, and output format are unresolved. Do not infer a particular external routing problem. Any concrete selection algorithm must be tied to explicitly stated assumptions. ### Clarifying Questions - Does proximity mean geographic distance, network latency, topology distance, or another score? - Which destinations are eligible, and are health and capacity constraints part of selection? - How are ties and the absence of an eligible destination handled? - Are inputs a fixed snapshot or changing while requests are routed? ```hint Filter before optimizing the score The nearest destination is useful only if it is allowed and able to serve the request under the declared policy. ``` ### What a Strong Answer Covers - A complete routing contract with proximity and eligibility distinguished. - A conditional baseline algorithm and data structures appropriate to the metric. - Deterministic ties, stale-state behavior, validation, and resource tradeoffs. ### Follow-up Questions - When would a spatial index help, and when would it be irrelevant? - How would you avoid routing every request to one nearby destination?