Disclaimer: this is my personal opinion and not the opinion of my colleagues or my employer.
We used to store Terra Bytes of data in ElasticSearch in form of JSON documents. As the size of data stored in cluster grew, we had to create new clusters with lots of nodes and it turned to a maintenance and cost nightmare. Microsoft Azure team suggested we move to DocumentDB to reduce the cost, and since it can scale infinitely, there won't be any maintenance needed. More...