Kaiyin Zhong — Data & AI platforms that hold their shape

Essays

math · pricing · statistics

Price fencing: the fence that sorts your customers for you

One price is a compromise nobody asked for: too high for the student, a gift to the procurement department, and usually both mistakes at once. A fence — an objective condition that costs the customer something — lets people sort themselves into price brackets without you ever guessing who is who. Here is what a single price actually costs, why the revenue curve is a lazy hill that hides your mistake, how much each extra fence is worth, what fences are made of, and how leaky a fence can get before it stops earning its keep.

Aug 3, 2026 · 15 min

Van Westendorp: four blunt questions and one elegant X Aug 3, 2026 Ask someone what a thing should cost and you get a shrug. Ask where the edges of acceptable are and they answer with startling consistency — which is the whole trick behind the price sensitivity meter, a method from 1976 that survives on four survey questions and no statistics at all. Here's how forty-eight scattered answers become four smooth curves, why two of them run the other way, where the famous smoothness actually comes from, and why the point labelled 'optimal' is the most dangerous number on the chart.
How to solve the 2D rectangle variant of the IQ fit puzzle: math and code Jul 26, 2026 Twelve ball-pieces, an 11×5 board of fifty-five holes, and one exact covering. Symmetry cuts the search space for free via the dihedral group, a counting argument proves that a full board is a solved board, and a Rust solver packs the whole grid into a single u64 so every placement is a bitwise AND.

Data, engineering, architecture. A decade of building data and ML platforms — research pipelines, production ML, and now LLM infrastructure as CDO at Swoep. I care most about the layer people skip: the foundation that decides whether everything on top of it actually works.