| Horde_Queue_Task |
| Horde_Queue_Runner | |
| Horde_Queue_Runner_RequestShutdown | |
| Horde_Queue_Storage | |
| Horde_Queue_Storage_Array | Stores queue tasks in the current request. No persistence. |
| Horde_Queue_Storage_Db | Stores queue tasks in a database table. |
| Horde_Queue_Storage_Sqs | Stores queue tasks in Amazon's SQS. |