SELECT 
  category_id, 
  parent_id 
FROM 
  categories 
WHERE 
  parent_id IN(
    20877, 20878, 20885, 20922, 20879, 20886, 
    20887, 20888, 20890, 20889, 20880, 
    20891, 20923, 20892, 20896, 20881, 
    20897, 20924, 20898, 20899, 20900, 
    20893, 20901, 20902, 20903, 20882, 
    20904, 20883, 20905, 20906, 20907, 
    20895, 20908, 20909, 20910, 20925, 
    20894, 20926, 20911, 20912, 20884, 
    20913, 20914, 20915, 20916, 20917, 
    20918, 20919, 20927, 20920, 20921
  )

Query time 0.00101

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "13.10"
    },
    "table": {
      "table_name": "categories",
      "access_type": "range",
      "possible_keys": [
        "parent"
      ],
      "key": "parent",
      "used_key_parts": [
        "parent_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 62,
      "rows_produced_per_join": 62,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "6.90",
        "eval_cost": "6.20",
        "prefix_cost": "13.10",
        "data_read_per_join": "162K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`goimagine`.`categories`.`parent_id` in (20877,20878,20885,20922,20879,20886,20887,20888,20890,20889,20880,20891,20923,20892,20896,20881,20897,20924,20898,20899,20900,20893,20901,20902,20903,20882,20904,20883,20905,20906,20907,20895,20908,20909,20910,20925,20894,20926,20911,20912,20884,20913,20914,20915,20916,20917,20918,20919,20927,20920,20921))"
    }
  }
}