SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    19373, 19374, 19375, 19376, 19377, 19378, 
    19379, 19380, 19381, 19382, 19383, 
    19384, 19385, 19386, 19387, 19388
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00220

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id", "idx_product_lang"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "lang_code"],
      "rows": 16,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (19373,19374,19375,19376,19377,19378,19379,19380,19381,19382,19383,19384,19385,19386,19387,19388) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}