We are trying to create an online-shopping like application in which we have to store a huge amount of data,since the data that will be stored are mostly document like data, the suggestion was to store the data in mongodb and using elasticsearch to add the search functionality, but i also know that elasticsearch itself can be used as a database to store the data, but I'm not sure if that's the right thing to do.Can you guys help me out?   
Storing data in elasticsearch vs mongodb
mongodb
Elastic search is a search index that looks like a db and mongo is a database with decent search capabilities too. I think the determinant should be your familiarity with the systems actually and if this is a greenfield project where you're diving into new technologies, you can minimize risk by using a more familiar technology like SQL instead of Mongo.If you do go the mongo + elastic search route, my only other advice would be to NOT try to use the mongo db river, and insert and update into elastic search using the regular old rest api. 