SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(1, 7, 2, 5, 6, 11)

Query time 0.00052

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_categories",
      "access_type": "ALL",
      "possible_keys": ["parent"],
      "rows": 13,
      "filtered": 69.2307663,
      "attached_condition": "cscart_categories.parent_id in (1,7,2,5,6,11)"
    }
  }
}

Result