And I've seen a system that did that. We had to predict what global aggregates we would need. Looking at a metric required finding the right instance to connect

And I've seen a system that did that. We had to predict what global aggregates we would need. Looking at a metric required finding the right instance to connect to if it wasn't in the bubbleup. Picking the right expressions to avoid double counts was hard. Want to do something fancy? No luck because of the lack of distributed querying.