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 (
    9803, 9805, 9797, 9800, 9798, 9801, 9802, 
    9806, 9804, 9809, 9810, 9811, 9812, 
    9807, 9808
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00055

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": 15,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (9803,9805,9797,9800,9798,9801,9802,9806,9804,9809,9810,9811,9812,9807,9808) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}