SELECT 
  * 
FROM 
  cscart_ec_pre_orders 
WHERE 
  storefront_id = 0

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.00"
    },
    "table": {
      "table_name": "cscart_ec_pre_orders",
      "access_type": "system",
      "possible_keys": [
        "PRIMARY"
      ],
      "rows_examined_per_scan": 1,
      "rows_produced_per_join": 1,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "0.00",
        "eval_cost": "0.20",
        "prefix_cost": "0.00",
        "data_read_per_join": "1K"
      },
      "used_columns": [
        "storefront_id",
        "preorder_text",
        "type",
        "price",
        "max_order",
        "max_order_qty",
        "choose_status",
        "notify_customer",
        "payment_methods",
        "starting_date",
        "ending_date",
        "timestamp",
        "shipping",
        "paid_status"
      ]
    }
  }
}