If you look at the code they used to have —postgres-dsn URL, now they changed it to —backend-dsn. If you go beyond the marketing, edgedb is a postgres connection pool+orm combined together with a query language (its a huge work in itself and commendable given it takes away many dependencies and provide a consistent developer experience). It’s leveraging postgresql server which is the true database providing ACID compliance.

Edgedb is more akin to hasura than to a database in traditional sense.