[{_id:1,"name":"user","email":"user@gmail.com","password":"***************","cart":[{"productId":"1253456912854","sizeQuantity":[{"size":"Large","quantity":2}]},{"productId":"1253456912855","sizeQuantity":[{"size":"Large","quantity":2},{"size":"X-Large","quantity":2}]}],"__v":0}]

db.collection.update({_id:1,"cart.productId":"1253456912854","cart.sizeQuantity.size":"Large"},{$set:{"cart.$[c].sizeQuantity.$[sq].quantity":4}},{arrayFilters:[{"c.productId":"1253456912854"},{"sq.size":"Large"}]})