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 (
    415299, 415298, 427777, 185446, 185442, 
    185439, 185433, 185435, 185438, 185441, 
    185456, 185443, 185436, 185448, 185447, 
    185452, 185449, 185434, 185437, 185445, 
    185440, 185450, 185454, 185451, 185455, 
    185444, 185453
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00147

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "37.86"
    },
    "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": 27,
      "rows_produced_per_join": 27,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "32.46",
        "eval_cost": "5.40",
        "prefix_cost": "37.86",
        "data_read_per_join": "184K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`webmarco`.`cscart_product_descriptions`.`product_id` in (415299,415298,427777,185446,185442,185439,185433,185435,185438,185441,185456,185443,185436,185448,185447,185452,185449,185434,185437,185445,185440,185450,185454,185451,185455,185444,185453)) and (`webmarco`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}