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 (
    12995, 12996, 12997, 12998, 15744, 15745, 
    15746, 15743, 15738, 15740, 15741, 
    15742, 15736, 15737, 12999, 13000, 
    13001, 13002, 13003, 13004
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00073

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 (12995,12996,12997,12998,15744,15745,15746,15743,15738,15740,15741,15742,15736,15737,12999,13000,13001,13002,13003,13004) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}