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 (
    41426, 1050, 2252, 3988, 36297, 2249, 
    41438, 353, 2260, 41018, 41230, 35475, 
    35470, 3984, 47486, 36465, 47608, 36299, 
    41439, 3985, 35471, 45597, 47428, 47614, 
    41440, 3616, 2044, 48551, 47612, 41431, 
    35685, 41434
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00549

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 (41426,1050,2252,3988,36297,2249,41438,353,2260,41018,41230,35475,35470,3984,47486,36465,47608,36299,41439,3985,35471,45597,47428,47614,41440,3616,2044,48551,47612,41431,35685,41434) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}