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 (
    2574, 1354, 284, 47008, 41404, 35925, 
    33606, 4105, 2089, 6363, 977, 15613, 
    40688, 1061, 1994, 3189, 5643, 41945, 
    29776, 2436, 37295, 1264, 4298, 15030, 
    27369, 28441, 290, 6469, 33464, 37298, 
    28442, 1516
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.02393

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 (2574,1354,284,47008,41404,35925,33606,4105,2089,6363,977,15613,40688,1061,1994,3189,5643,41945,29776,2436,37295,1264,4298,15030,27369,28441,290,6469,33464,37298,28442,1516) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}