Clickhouse is also crazy fast without materialized views - I've only done some PoC's against it, but in loading a largish data set of raw invoice CSVs, I was very impressed with the performance compared to our standard RDBMS.

that sounds like a non-canonical use of clickhouse. Wouldnt a good RDBMS be a better fit for invoice data? This is on the surface, of course, really interested in what is this invoice data like, and what queries are you trying to run on them.