Ent is a (proprietary) database wrapper library resembling an ORM,* but I don’t believe Facebook’s GraphQL server infrastructure is tied to Ent at all.
* Though Ent’s creators emphatically claim it is not an ORM, that phrase does give you a rough but directionally-accurate idea of what it is.
ah ok. sorry for potential misinformation, i glean only what i can from being a casual outside observer.