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 (
    12613, 12574, 12615, 12599, 12603, 12582, 
    12549, 12576, 12601
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00032

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": 9,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (12613,12574,12615,12599,12603,12582,12549,12576,12601) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}