I run a visa agency in Bali. The other half of my week goes into Apify Actors, and one of them merges the two big prediction markets into a single table: Kalshi, the CFTC-regulated US exchange, and Polymarket, the crypto-settled global one. Same field names for both, so you can sort the whole crowd-pricing board at once instead of writing two clients.

Merging two venues into one schema is mostly boring work — rename volumeNum to volume , agree on one date format. The part that is not boring is what happens when a field exists on one venue and not the other. You cannot leave a hole in a table, so you put a null in it. And then someone filters on that column.

Two filters, one board, mirror-image emptiness

On 23 October 2026 I ran the same request three times inside an hour. Both venues, markets mode, sorted by 24-hour volume, ten rows.…