One project I've used in the past is https://github.com/JerrySievert/mongolike https://github.com/JerrySievert/mongolike It provides a Mongo-like API directly

One project I've used in the past is https://github.com/JerrySievert/mongolike https://github.com/JerrySievert/mongolike It provides a Mongo-like API directly on Postgres, using normal tables/columns. I've used it in some projects in the past on some projects and it's fairly staightforward, and makes it easy to port an app from Mongo->Postgres.