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 (
    350, 1044, 351, 3992, 2155, 4373, 23481, 
    36474, 1358, 38136, 3981, 3982, 4383, 
    2248, 36303, 38151, 4384, 36302, 49186, 
    2247, 36308, 4376, 33809, 2152, 38553, 
    36301, 1847, 2251, 36305, 43651, 5632, 
    1841
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00661

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": 32,
          "filtered": 100,
          "index_condition": "cscart_product_descriptions.product_id in (350,1044,351,3992,2155,4373,23481,36474,1358,38136,3981,3982,4383,2248,36303,38151,4384,36302,49186,2247,36308,4376,33809,2152,38553,36301,1847,2251,36305,43651,5632,1841) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}