I wonder what will happen when you've 30 dimensions and you want to group by one of the 30 dimensions, then group by one of 30 dimensions then group by one of 30 dimensions. Is it possible to to do this stuff with counters?

Great article. We use Citus and have a very similar approach :)

The article mentions HLL, but there are even more useful extensions (e.g topn to handle tops through the jsonb format).