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 (
    13091, 12551, 12638, 12634, 12636, 12635, 
    12599, 12627, 12600, 12639, 15800, 
    12595, 12587, 12593, 12620, 12623, 
    12619, 12585, 12616, 12601
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00044

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": 20,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (13091,12551,12638,12634,12636,12635,12599,12627,12600,12639,15800,12595,12587,12593,12620,12623,12619,12585,12616,12601) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}