I'm using elastic search to index large amounts of sensor data for analytics purposes. The table has 4 million + rows and growing fast - expecting 40 million within the next year. This makes Elastic Search seem like a natural fit, especially with tools such as Kibana to easily display the data.
Elastic Search seems great, however there are are some more complex calculations that have to be performed as well. One such calculation is for our "average user time", where we take two data points (timestamp of item picked up and timestamp of item placed back), subtract them from each other and do an average of all these for one specific customer over a specific timeframe. The SQL query would look something like "select * from events where event_type = 'object picked up' or event_type = 'object placed back down'" then take all these events and get diffs on all their timestamps, add them all together then divide by count.
Our setup is: Rails, AngularJS, Elastic Search, Heroku, Postgres.