Is this not a little detailed for the architect exam. After all a deployment diagram is not part of the deliverables
I would guess that the design should avoid making assumptions for vendor specific features if possible, where unavoidable they should be stated in the assumptions.
The requirements usually indicate a need for scalability.
This is often done horizontally through clustering and therefore requires remote interfaces. Clustering doesn't always achieve an improvement in performance but it is one of the scalability features of J2EE that I guess the Sun people are looking for
I guess you don't even need to mention which method because as already mentioned, the lookup logic should be hidden behind a BusinessDelegate.
Just my two-penneth