How to know when you'll need more than one rabbit cluster?

[Paul Manno]

Hello,

Trying to understand when one message broker cluster isn't enough, not from a capacity standpoint, but from an architecture standpoint.  For example, say a company has product A and product B, both of which have the need for a message broker between the components of each product.  Would it be better to have a single rabbit cluster providing broker services for both A and B or would it be better for each to have it's own broker and thus not allow cross application external dependencies?  I'm kinda of the mind that each application stack should have it's own rabbit cluster since I feel like having one great big external dependency like that cross app stack is a bad architectural pattern.  Others in the company are not so sure and I'm just trying to understand what, if any,  best practices come into play here.

Thanks.

Paul M.