Outliers
Players whose recent numbers sit furthest from their own baseline — and the hand-rolled fetch whose race condition is worth reading about.
/outliers · src/composed/outliers
Ranks players by distance from their own recent baseline, so the board surfaces form that has moved rather than form that is merely good.
What it used to be
Worth knowing, because the shape recurs. The query was a hand-rolled
fetchOutliers: setLoading(true), an await fetch, setOutliers,
setError, finally setLoading(false) — fired from a useEffect behind a
500 ms setTimeout, keyed off a JSON.stringify of every filter and a
useRef holding the previous value of it.
Four pieces of state tracked what SWR already tracks, and a race was one slow response away: two in-flight requests resolved in arrival order, not request order, so a slow page 1 could overwrite a fast page 2.
What it is now
The lesson generalises: if you are holding a useRef of the previous filters to
decide whether to fetch, you have written a cache key by hand. Make it a key.
Value Bets
Model price against the market's, on three boards that run at once — and the URL-to-query mapping that has to exist on both sides of the network.
Bet Builder
Prices a multi-selection bet with correlation — fifteen queries and a model chain over them, and the deepest data graph in the product.