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 (
    4176, 4357, 4287, 4612, 4187, 4639, 4210, 
    4265, 4598, 4503, 4613, 4504, 4635, 
    4466, 4160, 4164, 4335, 4553, 4592, 
    4600, 4340, 4180, 4344, 4591, 4282, 
    4461, 4590, 4178, 4501, 4302, 4616, 
    4296, 4352, 4283, 4353
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00119

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "24.79"
    },
    "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": 35,
      "rows_produced_per_join": 35,
      "filtered": "100.00",
      "index_condition": "((`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_descriptions`.`product_id` in (4176,4357,4287,4612,4187,4639,4210,4265,4598,4503,4613,4504,4635,4466,4160,4164,4335,4553,4592,4600,4340,4180,4344,4591,4282,4461,4590,4178,4501,4302,4616,4296,4352,4283,4353)) and (`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "21.29",
        "eval_cost": "3.50",
        "prefix_cost": "24.79",
        "data_read_per_join": "159K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description",
        "unit_name"
      ]
    }
  }
}