Permissions duplication check mechanism

[FrioSea]

When recreating a permission that's just deleted on nacos console, it'll popup up an exception said "此角色权限已存在！".
After checking code, i found everytime you create a permission the console will invoke a duplication check first and within this check it will fetch the record from the buffer instead of database, somehow this buffer would only be freshed every 15 seconds, so if you recreate deleted permissions before this buffer get reloaded, you'll get the same exception.

My quesion is:
1.Why are we using this buffer instead of direct db query.
2.Could there be a refresh mechanism after every delete request.

1.Buffer
2.Duplication Check