Ditto. I don’t see how the size or complexity of the DB would have a direct correlation to framework choice.
> my boss is concerned about how CB will perform with a large complex DB (lots of tables, lots of joins, lots of records).
I would be more concerned with how well your database server will perform with a large complex DB.
If you are worried about high availability, ColdBox is very fast on it’s own and it used for some rather large sites handling a good deal of traffic such as http://tv.adobe.com/
There’s a larger (but slightly out-of-date) list here:
Point being, if you have a very complex site, ColdBox will not be what it slowing you down.