Postgres literally beats MongoDB at JSON in benchmarks. Y'know, the thing that's supposed to be Mongo's bread and butter?
Say you have some json and nested in it somewhere is an array of objects, and you want to just map over that and update those objects. I was writing a migration to do that in Postgres <11 once and it was not fun to try and figure out how to do it.
I haven't worked with Mongo in years though, so no clue how it has evolved since like 2015.
For example: they measured Query B execution time on postgres: 41m3s, mongodb: 1h13m3s. When MongoDB measured Query B with a supported driver, the execution time was only 3m30s more than 10x faster than postgres!
You'll find details here: https://www.mongodb.com/blog/post/benchmarking-do-it-right-o...