What amount of time is expected when deleting Knowledge Advanced documents?
Oracle Service Cloud, Product listing
The Knowledge Advanced content delete operation is not a simple. If the count of documents selected for deletion is more than 10 the delete happens through a batch job that runs every 15 minutes. However, if document selected is less than 10 then delete process is run immediately. When a content is deleted, all of its versions are deleted, all of its localized versions are deleted, and all association to user groups, categories and products are also deleted.
Processing time is relative to how many versions the content has, how many localizations they have etc.. In addition, if there is significant database processing running in the background with enough load to slow down processing as a whole, it has a direct impact on the time it will require to delete a particular content.
For further information see Answer ID 8156: Documentation for Oracle Service Cloud Knowledge Advanced