Little's Law is a theorem in queueing theory that the average number of items in a queue is equal to the average arrival rate multiplied by the average time the item spends in the queue.

Expressed in code, this looks like this

```
numberOfItemsInQueue = averageArrivalRate * averageTimeInQueue
```

## The interesting bit

Little's law show's us that this relationship is "not influenced by the arrival process distribution, the service distribution, the service order, or practically anything else." (src)

## Why this is important

If we know the average response times and total requests per second, we can estimate the maximum concurrent users on a web server. (src)