Queue Backlog and Drain Time Calculator
Estimate how many messages accumulate during a burst, then model recovery once the arrival rate falls. Use measured rates from the same queue and workload.
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Queue scenario
Rates are messages per second. The burst is modeled from an empty queue, followed by a steady arrival rate.
Formula and assumptions
Backlog = max(0, burst arrivals − service capacity) × burst seconds. Recovery time is backlog ÷ (post-burst service rate − steady arrivals).
This fluid estimate assumes constant rates, an initially empty queue, no retries or message-size differences, and unchanged service capacity after the burst. A non-positive net drain rate means the queue cannot catch up under the entered steady load. Compare against queue metrics and load-test results before capacity decisions.
Frequently asked questions
How is queue backlog estimated?
The positive excess of arrivals over processing, multiplied by burst seconds. It does not include backlog that existed before the burst.
When can a queue drain after a burst?
Only when processing capacity is greater than the continuing arrival rate. The difference is spare capacity available to clear queued messages.
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