SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    61415, 30752, 30738, 61431, 68844, 61417, 
    61421, 20378, 24474, 61437
  ) 
  AND cscart_product_descriptions.lang_code = 'ja'

Query time 0.00021

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id"],
      "key": "product_id",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 10,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (61415,30752,30738,61431,68844,61417,61421,20378,24474,61437)",
      "attached_condition": "cscart_product_descriptions.lang_code = 'ja'"
    }
  }
}