How I indexed 18,141 polynomial fan curves in Postgres and matched a duty point in 4 ms

If you work in building HVAC, you know the ritual. You need a fan that will push 5000 m³/h at 400 Pa. Your manufacturer rep emails you a 400 MB installer — usually Windows-only, often Delphi, almost always from 2007 — and you click through dialog boxes until the program picks a fan for you. The selection engine is a black box. You cannot embed it. You cannot query it. You cannot even link to a result. The math underneath is not complicated. It has been public for decades. It is just locked behin