SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    708, 689, 710, 490, 981, 642, 722, 656, 
    793, 615, 762, 596, 593, 972, 958, 1145, 
    986, 1158, 1076
  )

Query time 0.00064

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": 22,
          "filtered": 100,
          "index_condition": "cscart_categories.parent_id in (708,689,710,490,981,642,722,656,793,615,762,596,593,972,958,1145,986,1158,1076)"
        }
      }
    ]
  }
}