SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    5862, 5879, 5894, 6228, 6122, 5938, 5870, 
    5914, 6253, 6150, 5947, 5984, 5924, 
    5958, 5994, 6002, 6013, 6027, 6035, 
    6046, 6061, 6072, 6090, 6102, 6167, 
    6180, 6192, 6208, 6275
  )

Query time 0.00072

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "15.43"
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "range",
      "possible_keys": [
        "parent"
      ],
      "key": "parent",
      "used_key_parts": [
        "parent_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 36,
      "rows_produced_per_join": 36,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "8.24",
        "eval_cost": "7.20",
        "prefix_cost": "15.44",
        "data_read_per_join": "213K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`webmarco`.`cscart_categories`.`parent_id` in (5862,5879,5894,6228,6122,5938,5870,5914,6253,6150,5947,5984,5924,5958,5994,6002,6013,6027,6035,6046,6061,6072,6090,6102,6167,6180,6192,6208,6275))"
    }
  }
}