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Hi! Druid does not have the functionality to automagically make projections of one Druid dataset onto another just yet. In general it is common to think of your data in Druid as a projection of your raw data which lives in Kafka or S3 or something. In Druid this is referred to as Rollup (https://druid.apache.org/docs/latest/tutorials/tutorial-rollup.html). You can ingest your data only taking the dimensions you need and pre-aggregating the appropriate metrics for your analytic use cases. When doing it you will a single row in Druid representing multiple rows in your source data allowing for huge speedup/space saving (a rollup ratio of 30x is not uncommon). You could also ingest data multiple times (from the same source data), picking different sets of columns and getting different rollups for each dataset. It would then be up to you to route your queries accordingly to the different datasets you create.

Thanks for your input @Vadim!