SELECT 
  code 
FROM 
  cscart_zipcode_validator_list 
WHERE 
  product_id = 2015

Query time 0.00059

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "30.66"
    },
    "table": {
      "table_name": "cscart_zipcode_validator_list",
      "access_type": "ALL",
      "rows_examined_per_scan": 298,
      "rows_produced_per_join": 29,
      "filtered": "10.00",
      "cost_info": {
        "read_cost": "27.68",
        "eval_cost": "2.98",
        "prefix_cost": "30.66",
        "data_read_per_join": "1K"
      },
      "used_columns": [
        "product_id",
        "code"
      ],
      "attached_condition": "(`wearethehelpful_scalesta_net`.`cscart_zipcode_validator_list`.`product_id` = 2015)"
    }
  }
}