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 (
    41428, 1775, 37665, 2248, 41445, 5467, 
    3996, 35733, 5448, 951, 4363, 31732, 
    2256, 4268, 4267, 3994, 2247, 5775, 
    41616, 36496, 2251, 36271, 37545, 45282, 
    41007, 5771, 4001, 41410, 41010, 41411, 
    41226, 5447
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00246

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 (41428,1775,37665,2248,41445,5467,3996,35733,5448,951,4363,31732,2256,4268,4267,3994,2247,5775,41616,36496,2251,36271,37545,45282,41007,5771,4001,41410,41010,41411,41226,5447) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}