ArangoDB isn't designed to solve the same problems as ElasticSearch, it's a database/data store.
ElasticSearch is a search engine, first and foremost, and while you could use it as a database-of-first-resort, I'd be hesitant to recommend as much. For one thing, it doesn't take durability very seriously.
As a result, I have to assume you chose wisely if you're using ArangoDB for a standard database use-case.
Just wondering if you played with the hStore column in the postgres ways/nodes tables before diving into ArangoDB?
I see hStore as nosql-on-demand within a relational schema:
http://www.postgresql.org/docs/current/static/hstore.html
Nope we didn't, as I said in the post, it was one of the things we decided up front to use ArangoDB.
It is developed locally and we wanted to try if it scales up and assists us, or if we should go the "traditional" Postgres way that everybody else goes.
We didn't look into elastic search, since we wanted to give ArangoDB a try. We will have a look into it, thanks for the hint!