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 (
    41590, 41621, 34674, 48235, 6198, 15452, 
    15322, 6274, 34668, 30368, 47828, 277, 
    48503, 34667, 2859, 119, 27356, 31911, 
    118, 36272, 1323, 34669, 6355, 27262, 
    47824, 34666, 31910, 5992, 1765, 47600, 
    34675, 34670
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00484

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 (41590,41621,34674,48235,6198,15452,15322,6274,34668,30368,47828,277,48503,34667,2859,119,27356,31911,118,36272,1323,34669,6355,27262,47824,34666,31910,5992,1765,47600,34675,34670) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}