When we first started working with crossbar and autobahn we thought that realms would be a great way to separate clients. e.g. 1 realm per client/customer.
Further into development however, I've come to the conclusion that, realms are not a good means to separate clients/customers.
In order to add new clients/customers you'd have to shut down the router, modify the configuration then start the router back up again.
Shutting down might work for small applications but it wouldn't scale well at all.
Our current solution is to instead dedicate realms to system level separation, such as "system" for non client access, "portal" for customer based access and "integration" for 3rd party system level integration.
This pattern then makes sense to use domain based URIs to separate different customers in the various services which makes it much easier to add new customers versus or old way of dedicated realms.
I'm curious what other realm patterns the community has tried or is developing.