SELECT 
  product_id 
FROM 
  cscart_products 
WHERE 
  product_type = 'D'

Query time 0.00037

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "84.10"
    },
    "table": {
      "table_name": "cscart_products",
      "access_type": "ALL",
      "rows_examined_per_scan": 308,
      "rows_produced_per_join": 30,
      "filtered": "10.00",
      "cost_info": {
        "read_cost": "77.94",
        "eval_cost": "6.16",
        "prefix_cost": "84.10",
        "data_read_per_join": "147K"
      },
      "used_columns": [
        "product_id",
        "product_type"
      ],
      "attached_condition": "(`atulecarter_atul_demo7`.`cscart_products`.`product_type` = 'D')"
    }
  }
}