SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    23663, 23664, 23665, 23666, 23667, 23668, 
    23669, 23670, 23671, 23672, 23673, 
    23674, 23675, 23676, 23677, 23678
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00042

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 (23663,23664,23665,23666,23667,23668,23669,23670,23671,23672,23673,23674,23675,23676,23677,23678) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}