if a tasklist filter has refresh enabled, and if the filter uses a query that takes longer than the refresh period (which is 10 sec by default and is not configurable), the tasklist will continue to issue requests to the backend to query for the filter results, even if the last request has yet to complete.

This has the affect of swamping the database with requests to execute the same query, slowing down all such requests and leading to a situation that eventually pegs the CPU of the database instance and downs the service.