SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    10316, 10317, 10319, 10321, 10323, 10327, 
    10328, 10329, 10337, 10339, 10341, 
    10354, 10360, 10362, 10368, 10369
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00031

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 (10316,10317,10319,10321,10323,10327,10328,10329,10337,10339,10341,10354,10360,10362,10368,10369) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}