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 (
    33702, 37316, 37304, 37305, 33697, 33703, 
    37282, 33701, 37295, 37298, 37280, 
    37300, 37296, 37294, 41358, 37302, 
    37284, 41368, 41387, 41367, 37289, 
    37301, 33696, 37297, 37291, 37283, 
    37290, 41384, 37288, 37303
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.01195

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_descriptions",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "product_id"],
          "key": "PRIMARY",
          "key_length": "11",
          "used_key_parts": ["product_id", "lang_code"],
          "rows": 30,
          "filtered": 100,
          "index_condition": "cscart_product_descriptions.product_id in (33702,37316,37304,37305,33697,33703,37282,33701,37295,37298,37280,37300,37296,37294,41358,37302,37284,41368,41387,41367,37289,37301,33696,37297,37291,37283,37290,41384,37288,37303) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}