SELECT 
  variant_id, 
  yml2_unit 
FROM 
  cscart_product_feature_variant_descriptions 
WHERE 
  variant_id IN (
    '1', '125', '126', '367', '211', '462', 
    '473', '460', '1327', '1335', '1332', 
    '1293', '1304', '485', '487', '478', 
    '122', '121', '127', '439', '438', 
    '149', '246', '120', '124', '123', 
    '152', '461', '481', '479', '234', 
    '146', '483', '486', '480', '482', 
    '58', '147', '12', '14', '11', '10', 
    '8', '7', '26', '1294', '1295', '263', 
    '421', '422', '111', '1296', '313', 
    '237', '238', '475', '484', '469', 
    '467', '217', '232', '472', '477', 
    '170', '476', '165'
  ) 
  AND lang_code = 'ru'

Query time 0.00084

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "46.21"
    },
    "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": 66,
      "rows_produced_per_join": 66,
      "filtered": "100.00",
      "index_condition": "((`test_uchur_k`.`cscart_product_feature_variant_descriptions`.`variant_id` in ('1','125','126','367','211','462','473','460','1327','1335','1332','1293','1304','485','487','478','122','121','127','439','438','149','246','120','124','123','152','461','481','479','234','146','483','486','480','482','58','147','12','14','11','10','8','7','26','1294','1295','263','421','422','111','1296','313','237','238','475','484','469','467','217','232','472','477','170','476','165')) and (`test_uchur_k`.`cscart_product_feature_variant_descriptions`.`lang_code` = 'ru'))",
      "cost_info": {
        "read_cost": "39.61",
        "eval_cost": "6.60",
        "prefix_cost": "46.21",
        "data_read_per_join": "205K"
      },
      "used_columns": [
        "variant_id",
        "lang_code",
        "yml2_unit"
      ]
    }
  }
}