SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (2287, 512, 521, 2271, 2259) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00035

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "2.26"
    },
    "table": {
      "table_name": "cscart_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": 5,
      "rows_produced_per_join": 5,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "1.76",
        "eval_cost": "0.50",
        "prefix_cost": "2.26",
        "data_read_per_join": "22K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "unit_name"
      ],
      "attached_condition": "((`aomnia_com`.`cscart_product_descriptions`.`product_id` in (2287,512,521,2271,2259)) and (`aomnia_com`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}