[{"_id":"123","user":"name 1","point":208,},{"_id":"124","user":"name 2","point":215,},{"_id":"125","user":"name 3","point":185,}]

db.collection.aggregate([{$sort:{point:-1}},{$group:{"_id":null,"items":{"$push":"$$ROOT"}}},{"$unwind":{"path":"$items","includeArrayIndex":"items.rank"}},{"$replaceRoot":{"newRoot":"$items"}},{"$addFields":{"newRank":{"$add":["$rank",1]}}},{"$match":{_id:"125"}},])