SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    17577, 17578, 17579, 17580, 17581, 17582, 
    17583, 17584, 17585, 17586, 17587, 
    17588, 17589, 17590, 17591, 17592
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00040

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 (17577,17578,17579,17580,17581,17582,17583,17584,17585,17586,17587,17588,17589,17590,17591,17592) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}