SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    10680, 10681, 10682, 10683, 10684, 10685, 
    10686, 10687, 10688, 10692, 10693, 
    10694, 10699, 10702, 10704, 10705
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00125

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 (10680,10681,10682,10683,10684,10685,10686,10687,10688,10692,10693,10694,10699,10702,10704,10705) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}