> So if you have a companies table joined to a contacts table, you'd get a two element tuple with a list of companies and a list of contacts, and then you have to iterate to do the joins and turn it into a JSON tree.

Esqueleto has a function to avoid n+1's and return a map now:

https://hackage.haskell.org/package/esqueleto-3.5.3.0/docs/D...

https://www.foxhound.systems/blog/grouping-query-results-has...