@merklefabian using Crux-jdbc seems fairly straightforward approach for a crux app to use Heroku Postgres (I have not tried this though) https://opencrux.com/reference/jdbc.html

There also 3rd party libraries to use Redis with Crux instead of rocksdb

You may want to look at this issue regarding crux-jdbc https://clojurians.slack.com/archives/CG3AM2F7V/p1618845906228500?thread_ts=1618845906.228500&cid=CG3AM2F7V