The addition of the json type to databases like Postgres has significantly limited the usefulness of JSON-datastores like MongoDB for me. It used to be that if you had to store truly schema-less information, and wanted to be able to query it, you needed Mongo. Now, Postgres can do that inside of an otherwise structured table.
That said, there are applications for other less-structured datastores like Redis. When you need to store data with an expiration quickly, and use common datastructures like sets, Redis can be fantastic.
That said, there are applications for other less-structured datastores like Redis. When you need to store data with an expiration quickly, and use common datastructures like sets, Redis can be fantastic.