[{"_id":"random_id_1","priority":"P1","owners":["user-1","user-2"],},{"_id":"random_id_2","priority":"P1","owners":["user-1","user-2"],},{"_id":"random_id_3","priority":"P2","owners":["user-1","user-2"],}]

db.collection.aggregate([{"$match":{"priority":"P1"}},{"$facet":{"data":[{$addFields:{"group_by_owners":"$owners"}},{$unwind:"$group_by_owners"},{$group:{"_id":"$group_by_owners","total_items_in_group":{$sum:1},"items":{$push:"$$ROOT"}}},{$sort:{"total":-1}},{$unset:"items.group_by_owners"},{$project:{"_id":0,"group_key":"$_id","total_items_in_group":1,"limited_items":{$slice:["$items",1]}}},{"$limit":2}],"metadata":[{$count:"total_items_matched"}]}}])