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 (
    10206, 10209, 10216, 10203, 10204, 10205, 
    10207, 10208, 10210, 10211, 10212, 
    10213, 10215, 10217, 10218, 10219, 
    10220, 10221, 10222
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00039

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": 19,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (10206,10209,10216,10203,10204,10205,10207,10208,10210,10211,10212,10213,10215,10217,10218,10219,10220,10221,10222) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}