[threeseed]

I have used ElasticSearch also on a number of projects and it is an extremely simple to install, configure, use and manage. Most of the functions are trivially available over simple REST HTTP calls.

Unless you need basic search and you desperately want to keep everything in the same database I would split it out. Architecturally it makes more sense to split it out just to allow for different scaling needs.

[nugator]

From my experience Elasticsearch is far from trivial to configure right. At least compared to PostgreSQL.