Though Postgres is a great DB and supports JSON directly you get just a fraction of the query possibilities you have with Mongo. With Postgres you get some basi

Though Postgres is a great DB and supports JSON directly you get just a fraction of the query possibilities you have with Mongo. With Postgres you get some basic operations for the JSON data type (since the JSON support is added recently, think 12-18 months ago). So, I wouldn't consider it as a real substitute to Mongo.