Back in the 2010s pre-Rust era Facebook hired and acqui-hired some big names in the Haskell and functional programming world. Probably still have some of them,

Back in the 2010s pre-Rust era Facebook hired and acqui-hired some big names in the Haskell and functional programming world. Probably still have some of them, and their codebases. But Rust can probably now satisfy most of those use cases.