[{"_id":ObjectId("62622dd73905f04f59db2971"),"array1":[{"_id":"12","array2":[{"_id":"123","answeredBy":[]},{"_id":"124","answeredBy":[]}]}]}]

db.collection.update({"array1.array2._id":"123"},{$push:{"array1.$[].array2.$[inner].answeredBy":"success"}},{arrayFilters:[{"inner._id":"123"}]})