SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.meta_keywords, 
  cscart_product_descriptions.meta_description, 
  cscart_product_descriptions.search_words, 
  cscart_product_descriptions.promo_text, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    10668, 10669, 10670, 10671, 10672, 10673, 
    10674, 10675, 10676, 10677, 10679, 
    10680, 10681, 10682, 10683, 10684, 
    10685, 10686
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00127

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "lang_code"],
      "rows": 18,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (10668,10669,10670,10671,10672,10673,10674,10675,10676,10677,10679,10680,10681,10682,10683,10684,10685,10686) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}