Regarding your second point: your intuition seems good, as Alipay apparently extended Druid to performs joins this way, with good performance [1]. Unfortunately

Regarding your second point: your intuition seems good, as Alipay apparently extended Druid to performs joins this way, with good performance [1]. Unfortunately it looks like they won't finish open-sourcing it, but it at least validates the idea. [1] https://github.com/apache/incubator-druid/issues/6457 https://github.com/apache/incubator-druid/issues/6457