SELECT 
  ushop_product_descriptions.product_id, 
  ushop_product_descriptions.unit_name 
FROM 
  ushop_product_descriptions 
WHERE 
  ushop_product_descriptions.product_id IN (
    345, 346, 337, 321, 347, 323, 317, 326, 
    314, 327, 313, 324, 332, 316, 341, 333, 
    335, 339, 334, 336, 340, 343, 338, 342, 
    348, 344, 349
  ) 
  AND ushop_product_descriptions.lang_code = 'en'

Query time 0.00071

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "18.91"
    },
    "table": {
      "table_name": "ushop_product_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "9",
      "rows_examined_per_scan": 27,
      "rows_produced_per_join": 27,
      "filtered": "100.00",
      "index_condition": "((`marketplace`.`ushop_product_descriptions`.`product_id` in (345,346,337,321,347,323,317,326,314,327,313,324,332,316,341,333,335,339,334,336,340,343,338,342,348,344,349)) and (`marketplace`.`ushop_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "16.21",
        "eval_cost": "2.70",
        "prefix_cost": "18.91",
        "data_read_per_join": "171K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "unit_name"
      ]
    }
  }
}