SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    23343, 23344, 23345, 23346, 23347, 23348, 
    23349, 23350, 23351, 23352, 23353, 
    23354, 23355, 23356, 23357, 23358
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00149

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 (23343,23344,23345,23346,23347,23348,23349,23350,23351,23352,23353,23354,23355,23356,23357,23358) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}