Systems and methods for upgrading QoS levels of older transactions based on the presence of higher level QoS transactions in a given queue. A counter may be maintained to track the number of transactions in a queue that are assigned a corresponding QoS level. Each separate QoS level can have a corresponding counter. When a transaction is received by the queue, the counter corresponding to the QoS level of the transaction is incremented. When a transaction leaves the queue, the transaction is upgraded to the highest QoS level with a non-zero counter. Also, when the transaction leaves the queue, the counter corresponding to the original QoS level of the transaction is decremented.