SELECT 
  variant_id, 
  yml2_unit 
FROM 
  cscart_product_feature_variant_descriptions 
WHERE 
  variant_id IN (
    '1661', '523', '597', '1', '1737', '182', 
    '1672', '441', '1644', '1634', '1652', 
    '1715', '1649', '429', '1702', '1746', 
    '1706', '1708', '1748', '1642', '1671', 
    '433', '513', '1805', '1709', '1711', 
    '1712', '1670', '1669', '1665', '1667', 
    '1662', '1735', '1739', '1680', '1740', 
    '1682', '276', '1633', '1688', '1619', 
    '1714', '460', '1638', '447', '122', 
    '121', '440', '127', '439', '1349', 
    '362', '438', '149', '246', '120', 
    '1705', '1656', '279', '1716', '1668', 
    '1804', '430', '448', '1620', '442', 
    '1663', '1640', '1653', '1666', '1623', 
    '1635', '1713', '1738', '1630', '1645', 
    '1677', '1658', '1741', '1664', '146', 
    '431', '446', '59', '50', '58', '147', 
    '98', '280', '469', '1673', '1637', 
    '1627', '1629', '206', '170', '1646', 
    '1628', '165'
  ) 
  AND lang_code = 'ru'

Query time 0.00100

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "69.31"
    },
    "table": {
      "table_name": "cscart_product_feature_variant_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "variant_id",
        "lang_code"
      ],
      "key_length": "9",
      "rows_examined_per_scan": 99,
      "rows_produced_per_join": 99,
      "filtered": "100.00",
      "index_condition": "((`test_uchur_k`.`cscart_product_feature_variant_descriptions`.`variant_id` in ('1661','523','597','1','1737','182','1672','441','1644','1634','1652','1715','1649','429','1702','1746','1706','1708','1748','1642','1671','433','513','1805','1709','1711','1712','1670','1669','1665','1667','1662','1735','1739','1680','1740','1682','276','1633','1688','1619','1714','460','1638','447','122','121','440','127','439','1349','362','438','149','246','120','1705','1656','279','1716','1668','1804','430','448','1620','442','1663','1640','1653','1666','1623','1635','1713','1738','1630','1645','1677','1658','1741','1664','146','431','446','59','50','58','147','98','280','469','1673','1637','1627','1629','206','170','1646','1628','165')) and (`test_uchur_k`.`cscart_product_feature_variant_descriptions`.`lang_code` = 'ru'))",
      "cost_info": {
        "read_cost": "59.41",
        "eval_cost": "9.90",
        "prefix_cost": "69.31",
        "data_read_per_join": "308K"
      },
      "used_columns": [
        "variant_id",
        "lang_code",
        "yml2_unit"
      ]
    }
  }
}