Since it is not possible to find \"blueberry\" by the word \"blue\" by using a mongodb full text search, I want to help my users to complete the word \"blue\" to \"blueberry\".
For those who have not yet started implementing any database architecture and are here for a solution, go for Elasticsearch. Its a json document driven database similar to mongodb structurally. It has "edge-ngram" analyzer which is really really efficient and quick in giving you did you mean for mis-spelled searches. You can also search partially.