Estimate queue wait time from arrival rate, service rate and worker count.
Wait time rises non-linearly with utilisation, staying negligible until about 70 per cent and then climbing steeply. That is why systems run at 80 per cent utilisation feel fine and systems at 95 per cent feel broken. The practical consequence is that spare capacity is not waste but the mechanism that keeps latency predictable.
Job Queue Wait Time
Wait ≈ ρ × service time ÷ (workers × (1 − ρ)) where ρ is utilisation
Wait ≈ ρ × service time ÷ (workers × (1 − ρ)) where ρ is utilisation Wait time rises non-linearly with utilisation, staying negligible until about 70 per cent and then climbing steeply. That is why systems run at 80 per cent utilisation feel fine and systems at 95 per cent feel broken.
The practical consequence is that spare capacity is not waste but the mechanism that keeps latency predictable.
This calculator takes 4 inputs: Jobs arriving per second, Average service time, Workers, Existing queue depth. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.