Database
[{"users":[{"_id":{"$oid":"61441890a6566a001623b8ed"},"name":"Jollibee",},{"_id":{"$oid":"61441890a6566a001623b8ed"},"name":"Jollibee",},{"_id":{"$oid":"61441890a6566a001623b8ed"},"name":"MCDO",},{"_id":{"$oid":"61441890a6566a001623b8ed"},"name":"Burger King",},]}]
Query
db.collection.aggregate([{"$unwind":"$users"},{"$group":{"_id":"$users.name","count":{"$sum":1}}},{"$match":{"_id":{"$ne":null},"count":{"$gt":1}}}])