SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    2805, 2806, 2807, 2808, 2529, 2530, 2531, 
    2532, 2809, 2810, 2811, 2812, 2813, 
    2814, 2815, 2816, 2817
  )

Query time 0.00017

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_categories",
      "access_type": "range",
      "possible_keys": ["parent"],
      "key": "parent",
      "key_length": "3",
      "used_key_parts": ["parent_id"],
      "rows": 17,
      "filtered": 100,
      "index_condition": "cscart_categories.parent_id in (2805,2806,2807,2808,2529,2530,2531,2532,2809,2810,2811,2812,2813,2814,2815,2816,2817)"
    }
  }
}