SELECT 
  variant_id, 
  yml2_unit 
FROM 
  cscart_product_feature_variant_descriptions 
WHERE 
  variant_id IN (
    '1', '3', '366', '125', '367', '1308', 
    '374', '379', '383', '391', '122', 
    '127', '438', '149', '120', '270', 
    '146', '50', '57', '147', '237', '257', 
    '376', '170'
  ) 
  AND lang_code = 'kk'

Query time 0.00038

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "16.81"
    },
    "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": 24,
      "rows_produced_per_join": 24,
      "filtered": "100.00",
      "index_condition": "((`test_uchur_k`.`cscart_product_feature_variant_descriptions`.`variant_id` in ('1','3','366','125','367','1308','374','379','383','391','122','127','438','149','120','270','146','50','57','147','237','257','376','170')) and (`test_uchur_k`.`cscart_product_feature_variant_descriptions`.`lang_code` = 'kk'))",
      "cost_info": {
        "read_cost": "14.41",
        "eval_cost": "2.40",
        "prefix_cost": "16.81",
        "data_read_per_join": "74K"
      },
      "used_columns": [
        "variant_id",
        "lang_code",
        "yml2_unit"
      ]
    }
  }
}