SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    300, 303, 304, 305, 306, 307, 308, 309, 
    310, 311, 312, 313, 314, 315, 316
  ) 
  AND cscart_product_descriptions.lang_code = 'da'

Query time 0.00047

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "36.01"
    },
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "9",
      "rows_examined_per_scan": 15,
      "rows_produced_per_join": 15,
      "filtered": "100.00",
      "index_condition": "((`atulecarter_atul_demo1`.`cscart_product_descriptions`.`product_id` in (300,303,304,305,306,307,308,309,310,311,312,313,314,315,316)) and (`atulecarter_atul_demo1`.`cscart_product_descriptions`.`lang_code` = 'da'))",
      "cost_info": {
        "read_cost": "33.01",
        "eval_cost": "3.00",
        "prefix_cost": "36.01",
        "data_read_per_join": "68K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "unit_name"
      ]
    }
  }
}