SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    490, 491, 492, 494, 495, 496, 497, 498, 
    499, 500, 501, 502, 503, 504, 506, 507, 
    508, 510, 511
  )

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_categories",
          "access_type": "range",
          "possible_keys": ["parent"],
          "key": "parent",
          "key_length": "3",
          "used_key_parts": ["parent_id"],
          "rows": 19,
          "filtered": 100,
          "index_condition": "cscart_categories.parent_id in (490,491,492,494,495,496,497,498,499,500,501,502,503,504,506,507,508,510,511)"
        }
      }
    ]
  }
}