Ah, I see, that makes sense. Usually pulling both tables in full (or even a single table in full) to the client is not an option (and nobody does cross products

Ah, I see, that makes sense. Usually pulling both tables in full (or even a single table in full) to the client is not an option (and nobody does cross products in real-time systems). So people end up pulling a subset of table A, and then for each document in the subset issue a separate get to the db for table B (which is obviously worse than having the db do it).