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 (
    2474, 33695, 37944, 4808, 2744, 1064, 
    41370, 26867, 36295, 2158, 37307, 4872, 
    4806, 41356, 41373, 31945, 41369, 37299, 
    43461, 33698, 41366, 35690, 32307, 
    37292, 45569, 41402, 43842, 37281, 
    47622, 37286, 43841, 33700
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00674

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 (2474,33695,37944,4808,2744,1064,41370,26867,36295,2158,37307,4872,4806,41356,41373,31945,41369,37299,43461,33698,41366,35690,32307,37292,45569,41402,43842,37281,47622,37286,43841,33700) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}