SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    372, 92, 28, 356, 21, 375, 86, 118, 3343, 
    3500, 3501
  )

Query time 0.00039

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": 32,
      "filtered": 100,
      "index_condition": "cscart_categories.parent_id in (372,92,28,356,21,375,86,118,3343,3500,3501)"
    }
  }
}