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 (
    35930, 20625, 41017, 3720, 41825, 5729, 
    41404, 35925, 5733, 15613, 48849, 37295, 
    41407, 4298, 15030, 4393, 6469, 37298, 
    6047, 1850, 6480, 5722, 35923, 2626, 
    37280, 4282, 1833, 24707, 4289, 6066, 
    273, 36568
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.02162

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 (35930,20625,41017,3720,41825,5729,41404,35925,5733,15613,48849,37295,41407,4298,15030,4393,6469,37298,6047,1850,6480,5722,35923,2626,37280,4282,1833,24707,4289,6066,273,36568) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}