[{"_id":ObjectId("5ce7335c1c666f000414f74a"),"event_id":ObjectId("5cb54f966668a9719ef6a103"),"subtotal":3000,"service_fee":760,"processing_fee":143,"total":3903,"customer_id":ObjectId("5ce7666c1c335f000414f747"),"updated_at":ISODate("2019-05-23T23:57:17.524Z"),"created_at":ISODate("2019-05-23T23:57:17.524Z"),"ref":"60d5fcf9-86c6-469b-b86b-315a9b55caca","issued_tickets":[{"_id":ObjectId("5ce7335c1c335f000414f666"),"name":"Tier 1","stub_name":"Tier 1","price":1500,"base_fee":200,"perc_fee":"0.12","access_code":"163a1b9ee98338a8a4288a1c87446665","redeemed":false},{"_id":ObjectId("5ce7335c1c335f0004146669"),"name":"Tier 1","stub_name":"Tier 1","price":1500,"base_fee":200,"perc_fee":"0.12","access_code":"f50f262cd0bf1ec4ab36667c2a762446","redeemed":true}]}]

db.collection.aggregate([{$unwind:"$issued_tickets"},{$group:{_id:{_id:"$event_id",ticketName:"$issued_tickets.name"},count:{$sum:1}}},{$project:{event_id:"$_id._id",ticketName:"$_id.ticketName",count:1,_id:0}}])