SELECT 
  shipping_id 
FROM 
  cscart_shippings 
WHERE 
  service_id = 714 
LIMIT 
  1

Query time 0.00013

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.28"
    },
    "table": {
      "table_name": "cscart_shippings",
      "access_type": "ALL",
      "rows_examined_per_scan": 6,
      "rows_produced_per_join": 1,
      "filtered": "16.67",
      "cost_info": {
        "read_cost": "1.18",
        "eval_cost": "0.10",
        "prefix_cost": "1.28",
        "data_read_per_join": "2K"
      },
      "used_columns": [
        "shipping_id",
        "service_id"
      ],
      "attached_condition": "(`kcoffee`.`cscart_shippings`.`service_id` = 714)"
    }
  }
}