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 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    431070, 431433, 431397, 431370, 430783, 
    430775, 431432, 431286, 431306, 431490, 
    431268, 431493, 431398, 431444, 431386, 
    431305, 430763, 431255, 430967, 431254, 
    431399, 431484, 435512, 430776, 430784, 
    431016, 431173, 431216, 431318, 431417, 
    431371, 431416, 435513, 430729, 431272, 
    431319, 431372, 431461, 431373, 431271, 
    435515, 435514, 431267, 431269, 435516, 
    431270, 387051, 435517, 435518, 432250
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00317

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "70.09"
    },
    "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": 50,
      "rows_produced_per_join": 50,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "60.10",
        "eval_cost": "10.00",
        "prefix_cost": "70.10",
        "data_read_per_join": "341K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`webmarco`.`cscart_product_descriptions`.`product_id` in (431070,431433,431397,431370,430783,430775,431432,431286,431306,431490,431268,431493,431398,431444,431386,431305,430763,431255,430967,431254,431399,431484,435512,430776,430784,431016,431173,431216,431318,431417,431371,431416,435513,430729,431272,431319,431372,431461,431373,431271,435515,435514,431267,431269,435516,431270,387051,435517,435518,432250)) and (`webmarco`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}