SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    22303, 22304, 22305, 22306, 22307, 22308, 
    22309, 22310, 22311, 22312, 22313, 
    22314, 22315, 22316, 22317, 22318
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00033

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 (22303,22304,22305,22306,22307,22308,22309,22310,22311,22312,22313,22314,22315,22316,22317,22318) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}