[{"_id":{"$oid":"60dd5e0bd0ba24343dabc626"},"s":{"_71vnohpi4":{"q":2}}},{"_id":{"$oid":"609ea0b0c85ca8e54adc610c"},"s":{"_71vnohpi4":{"q":49},"_h2121audz":{"q":20}}}]

db.collection.aggregate([{$project:{s:{$objectToArray:"$s"}}},{$unwind:"$s"},{$group:{_id:"$s.k",count:{$sum:"$s.v.q"}}},{$group:{_id:null,s:{$push:{k:"$_id",v:{q:"$count"}}}}},{$project:{s:{$arrayToObject:"$s"}}}])