If you already have PostgreSQL and only need limited indexing against the JSON, I'd use that... If you're looking for a document datastore for HA and/or read/write scaling, then I'd look at RethinkDB or MongoDB. I like RethinkDB better (as do many), it's currently pretty stable, I'm hoping to see some development pick up. There was some scare late last year as the backing company shuttered, but it's now under the Linux Foundation, so should see continued support.