Recoil
Meta's state-management library — popularised the "atom" + "selector" pattern. Archived January 2025 after the lead developer left Meta.
Dave McMurray + Meta team built it 2020 for internal use at Facebook. Inspired Jotai (Daishi Kato built his variant). No longer maintained — use Jotai or Zustand instead. Still lives in many codebases from the 2020-2022 era.