SELECT 
  category_id, 
  parent_id 
FROM 
  categories 
WHERE 
  parent_id IN(
    21794, 21777, 21778, 21793, 21792, 21779, 
    21780, 21623, 23117, 21673, 21676, 
    21679, 21680, 21677, 21771, 23114, 
    21629, 21742, 21743, 21772, 21622, 
    21735, 21776, 22618, 21788, 21786, 
    21607, 21797, 21761, 22898, 21631, 
    21787, 23013, 22616, 21791, 21785, 
    22625, 21796, 21744, 21996, 23008, 
    23091, 21989, 22617, 21979, 21800, 
    23014, 21798, 21762, 21630, 22619, 
    21678, 21675, 21988, 21632, 21672, 
    23115, 21773, 21763, 21741, 21987, 
    21674, 21795, 23012
  )

Query time 0.00099

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "19.28"
    },
    "table": {
      "table_name": "categories",
      "access_type": "range",
      "possible_keys": [
        "parent"
      ],
      "key": "parent",
      "used_key_parts": [
        "parent_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 93,
      "rows_produced_per_join": 93,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "9.98",
        "eval_cost": "9.30",
        "prefix_cost": "19.28",
        "data_read_per_join": "243K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`goimagine`.`categories`.`parent_id` in (21794,21777,21778,21793,21792,21779,21780,21623,23117,21673,21676,21679,21680,21677,21771,23114,21629,21742,21743,21772,21622,21735,21776,22618,21788,21786,21607,21797,21761,22898,21631,21787,23013,22616,21791,21785,22625,21796,21744,21996,23008,23091,21989,22617,21979,21800,23014,21798,21762,21630,22619,21678,21675,21988,21632,21672,23115,21773,21763,21741,21987,21674,21795,23012))"
    }
  }
}