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Medium · data_structures · Quant Developer interview question · robin-hood, open-addressing, hash-map, data_structures, probe-distance, linear-probing
Low-latency order routers cache per-instrument routing metadata (venue IDs, fee tiers, lot sizes) in a hash map that must survive high load factors without degrading to O(n) worst-case lookups. Robin Hood hashing solves this by redistributing probe sequences during insertion: when inserting an entry, if its current probe distance exceeds the probe distance of the slot's existing occupant (the 'rich' entry with a short path), we steal the slot and continue inserting the displaced entry. This bala