BuddyPress.org

… views and on the fly queries are very computationally expensive

Once the initial activity array has been built via query, the array can be appended to with each new reportable activity—as the data is being written to the appropriate table. The only time the system would need to be queried again is during a site reset, or for periodic purposes of clearing the cache. The time interval between cache clearing could be configurable via a Site Admin option.

With fewer writes required—records are written to the component table(s) and not to an activity table as well— performance could actually improve.