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, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    19932, 14056, 18508, 18520, 18571, 14112, 
    14092, 14080, 14066, 14050, 14049, 
    19603, 14091, 14123, 14079, 14090, 
    14122, 14089, 19711, 19947, 14065, 
    14102, 14064, 14063
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00037

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.04252208,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_descriptions",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "product_id"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["product_id", "lang_code"],
          "loops": 1,
          "rows": 24,
          "cost": 0.04252208,
          "filtered": 100,
          "attached_condition": "cscart_product_descriptions.product_id in (19932,14056,18508,18520,18571,14112,14092,14080,14066,14050,14049,19603,14091,14123,14079,14090,14122,14089,19711,19947,14065,14102,14064,14063) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}