Scalelite appears like a BigBlueButton server for other API consumers. Thus, for Greenlight doesn't need to know anything about the BigBlueButton servers which are "behind" the Scalelite service.
Scalelite forwards room create requests to the "least used" BigBlueButton server and then keeps track of which sessions run on which server and how many users are on there. When a user join request gets sent over API to Scalelite, it forwards the user to the BBB server which currently hosts that target session.
Greenlight and Scalelite can be installed on the same (virtual) machine, and unless you use the recording feature or have many thousands of concurrent users, Greenlight and Scalelite don't need much CPU/RAM/disk space.
You can also set up a bunch of different Greenlight instances and make them all use the same Scalelite (and the BBB servers behind that).
Best regards,
basisbit