Python mostly, and Java if you are using Flink. We do both. The thing with Scala is, it's mostly linked to Spark, and then probably a good portion of the gigs out there using Spark are using Databricks, and Databricks is pretty expensive, so people are moving away from it. At least this has been my case for two companies -- one moved to self-host Vertica and the other is about to move to Flink.
