SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    20197, 20198, 20199, 20200, 20204, 20205, 
    20206, 20207, 20211, 20212, 20216, 
    20217, 20218, 20219, 20220, 20221, 
    20226, 20227, 20228, 20229, 20230, 
    20231, 20232, 20233, 20234, 20235, 
    20236, 20237, 20238, 20239, 20240, 
    20244, 20245, 20246, 20250, 20251, 
    20252, 20253, 20258, 20265, 20266, 
    20267, 20268, 20269, 20275, 20276, 
    20277, 20278, 20279, 20280, 20281, 
    20282, 20283
  ) 
  AND category_id != 1

Query time 0.00006

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_categories",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "parent", "p_category_id"],
          "key": "parent",
          "key_length": "3",
          "used_key_parts": ["parent_id"],
          "rows": 78,
          "filtered": 100,
          "index_condition": "cscart_categories.parent_id in (20197,20198,20199,20200,20204,20205,20206,20207,20211,20212,20216,20217,20218,20219,20220,20221,20226,20227,20228,20229,20230,20231,20232,20233,20234,20235,20236,20237,20238,20239,20240,20244,20245,20246,20250,20251,20252,20253,20258,20265,20266,20267,20268,20269,20275,20276,20277,20278,20279,20280,20281,20282,20283)",
          "attached_condition": "cscart_categories.category_id <> 1"
        }
      }
    ]
  }
}