SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    216, 204, 210, 212, 211, 213, 209, 217, 
    215, 214, 208, 218
  )

Query time 0.00031

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": 15,
          "filtered": 100,
          "index_condition": "cscart_categories.parent_id in (216,204,210,212,211,213,209,217,215,214,208,218)"
        }
      }
    ]
  }
}