Any sufficiently relational query... Try and generate dynamic reports on data, or an aggregation on an aggregation. The model subtly breaks even on simple ques

Any sufficiently relational query... Try and generate dynamic reports on data, or an aggregation on an aggregation. The model subtly breaks even on simple questions like "I want to know all users who are currently logged in and the contents of their feed right now, with the last 5 messages they sent". You basically have to do multiple requests, MULTI, or write a lua script to get all this to happen in a transaction (so the state of the world is consistent). Such a request is trivial in relational databases, though performance of the query may not be.