Database
[{"_id":ObjectId("5dc1c8f2e3341fc38ef47698"),"productCode":"123456","sizes":[{"size":"35","wares":[{"ware":"LAX","amount":"0","reserved":"0","incoming":"0"},{"ware":"NYC","amount":"0","reserved":"0","incoming":"0"}],"ean":"5057794020269"},{"size":"36","wares":[{"ware":"LAX","amount":"0","reserved":"0","incoming":"0"},{"ware":"NYC","amount":"0","reserved":"0","incoming":"0"}]}]}]
Query
db.collection.update({"productCode":"123456"},{"$set":{"sizes.$[e1].wares.$[e2].reserved":"2"}},{arrayFilters:[{"e1.size":"35"},{"e2.ware":"NYC"}]})