SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.short_description, 
  IF(
    cscart_product_descriptions.short_description = '' 
    OR cscart_product_descriptions.short_description IS NULL, 
    cscart_product_descriptions.full_description, 
    ''
  ) AS full_description, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    6426, 6428, 8800, 6255, 6394, 6229, 6256, 
    8576, 6189, 6257, 6259, 6145, 6332, 
    6362, 5644, 6226, 6279, 6392, 8577, 
    6297, 6354, 6278, 6331, 6337, 6395, 
    6423, 6427, 6364, 8569, 6190, 6276, 
    6303, 6359, 6429, 6280, 6260, 6305, 
    6330, 6434, 6355
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00117

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "28.33"
    },
    "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": 40,
      "rows_produced_per_join": 40,
      "filtered": "100.00",
      "index_condition": "((`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_descriptions`.`product_id` in (6426,6428,8800,6255,6394,6229,6256,8576,6189,6257,6259,6145,6332,6362,5644,6226,6279,6392,8577,6297,6354,6278,6331,6337,6395,6423,6427,6364,8569,6190,6276,6303,6359,6429,6280,6260,6305,6330,6434,6355)) and (`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "24.33",
        "eval_cost": "4.00",
        "prefix_cost": "28.33",
        "data_read_per_join": "182K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description",
        "unit_name"
      ]
    }
  }
}