We were doing some benchmarks recently on different databases. Most of the queries were heavy aggregations (>1billion of rows) and, to be honest, we were a bit disappointed with the new parallel query support in pg, we were expecting much better performance.

While doing the benchmarks, we could see that citus was always taking full advantage of all the cores in the cluster, while postgres parallelization was not.

Disclaimer: I'm not a db expert and I don't have any relationship with either citus or postgres.