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

Query time 0.00006

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_categories",
      "access_type": "ALL",
      "possible_keys": ["parent"],
      "rows": 83,
      "filtered": 21.6867466,
      "attached_condition": "cscart_categories.parent_id in (210,212,216,204,211,213,209,217,215,214,218,208)"
    }
  }
}