The corpus meta answers in milliseconds, from season rollups

A corpus-wide card or deck meta read scanned every recorded battle on every call - 8 to 13 seconds warm, and nine timeouts a week. The record now keeps one rollup per season and mode (deck, card by form, card pair, and the totals every rate is a share of), rebuilt nightly from the raw rows and topped up hourly with the battles recorded since. battles_meta_decks, battles_meta_cards and cards_synergy read it whenever the window is exactly one season, which is their default; the response carries players_as_of and a note, because distinct-player counts are as of the last rebuild and the counters trail by up to an hour. A clan, player or collection read, and any explicit window, still scan the raw rows exactly as before and only take the corpus prior from the rollup. Contract 3.11.0.