Tag based document in MongoDB

I am working in a large dataset. using embedded document structure, I would like to know how i can implement tagging in inner document to improve performance. I saw some tagging related document but not in embedded document specially inner arrays. Example:

company {
   _id: xxxx,
         name: renjith,
         design: developer
         name: varun,
         design: lead

How i can add tags inside employees array with fast retrieval.