SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.search_words, 
  cscart_product_descriptions.short_description, 
  cscart_product_descriptions.full_description, 
  cscart_product_descriptions.meta_description, 
  cscart_product_descriptions.meta_keywords, 
  cscart_product_descriptions.page_title, 
  cscart_product_descriptions.promo_text, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (12855, 12856, 12551) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00145

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": 3,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (12855,12856,12551) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id search_words short_description full_description meta_description meta_keywords page_title promo_text unit_name
12551 <p><iframe width="560" height="315" src="https://www.youtube.com/embed/tMA7wWKExJw" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen=""></iframe></p>
12855
12856