SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    22431, 22432, 22433, 22434, 22435, 22436, 
    22437, 22438, 22439, 22440, 22441, 
    22442, 22443, 22444, 22445, 22446
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id", "idx_product_lang"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "lang_code"],
      "rows": 16,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (22431,22432,22433,22434,22435,22436,22437,22438,22439,22440,22441,22442,22443,22444,22445,22446) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}