[{clientName:"client1",employees:[{"employeename":1,"configuration":{"isAdmin":true,"isManager":false}},{"employeename":2,"configuration":{"isAdmin":false,"isManager":false}}]}]

db.collection.aggregate([{"$match":{"clientName":"client1"}},{"$set":{"employees":{"$filter":{"input":"$employees","cond":{"$eq":["$$this.configuration.isAdmin",true]}}}}}])