Thanks Boxuan, Marc, and Eric.

I implemented Boxuan's get-vertex-ids-and-delete-in-parallel suggestion with 8 gremlinpython workers, and it saves an order of magnitude of time.  I imagine it could scale up further with more parallelism.  That's some great time savings, thank you!

Marc, good idea to snapshot and then do full down-and-up.  I assume we'd have to take down Cassandra and Elasticsearch as well, and then start their docker images back up with substituted volumes.  This would obviously be outperform for millions/billions of vertices.

Eric, it sounds like your approach may while keeping the data store (e.g., Cassandra) and indexer (e.g., Elasticsearch) alive, which could improve efficiency over a full tear-down.  We'll consider this as well, probably identifying some docker-based analogs for some of the janusgraph shell commands.  Thanks!