Then what's up with the pattern they show of querying every board and then iterating through to query again for every report associated with the board?
I was expecting them to say after introducing this, that they started with an intentionally bad example so they could improve on it. But instead they went on to talk about a 2.5x speedup on something that would already be 100x faster in any other database. I don't get why they're doing this at all.