Thanks for sharing this - the architecture is really impressive and it's great to see Livy leveraged in this way!

I experimented with a similar design a couple of years ago but one problem I had with Livy was the fact that it doesn't support concurrent queries within the same session (https://issues.apache.org/jira/browse/LIVY-544), even when the FAIR scheduler is activated.

Is this something you also modified? Because for interactive use-cases (especially in a notebook-based environment) users might want to run more than one query at a time.