This is quite confusing - you shouldn’t need a columnar engine to filter/aggregate 20k rows. Postgres / MySQL with a table per board (or one giant partitioned

This is quite confusing - you shouldn’t need a columnar engine to filter/aggregate 20k rows. Postgres / MySQL with a table per board (or one giant partitioned table with a JSONb column) would have been totally fine, as would have one SQLite database per customer that you can load the initial page of and then ship the whole thing to the client for richer interactivity.