I suppose the takeaway is meant to be: why bother having two separate data storage systems (relational + schemaless) if only one will do? I mean, if Mongo isn

I suppose the takeaway is meant to be: why bother having two separate data storage systems (relational + schemaless) if only one will do? I mean, if Mongo isn't offering much (if any) performance gain or schemaless flexibility... what's the advantage? With Postgres, you can have your cake and eat it: your transactional data gets the benefits of a strict schema and referential integrity, but you also get an "escape hatch" out of the relational model for when that is needed. (And 18 years of proven code, deployed at massive scale, that definitely isn't going to lose your data.) Side note: what's with Mongo using so much storage? Perhaps an append-only log without garbage collection?