> ## Documentation Index
> Fetch the complete documentation index at: https://docs.breakscale.tech/llms.txt
> Use this file to discover all available pages before exploring further.

# Rate limited API

> Turning excess away before it queues

A limiter refuses excess traffic at the door. It serves slightly less, but what it does serve stays fast instead of queueing.

## What to watch

The limiter does not add capacity. It refuses some requests quickly so the rest are answered quickly: at 600 offered it serves 200 at 36ms, where removing it serves 234 at 235ms. Saying no fast is what buys the predictable wait.

## What it is made of

| Component    | Count |
| ------------ | ----: |
| Client       |     1 |
| Database     |     1 |
| Rate limiter |     1 |
| Service      |     1 |

## Under load

Measured by running this design through the simulator at multiples of its own offered rate of 150 requests a second. Twenty seconds of simulated time, one fixed seed, so the same numbers come out every time.

<Note>This design holds 150 requests a second with 0% errors. At 225 it is losing 5% of them.</Note>

| Offered | Goodput |    p99 | Errors |
| ------: | ------: | -----: | -----: |
|     150 |     148 | 81.8ms |     0% |
|     225 |     193 | 85.7ms |   5.4% |
|     300 |     197 | 81.9ms |  34.9% |
|     375 |     202 | 83.1ms |  46.9% |
|     450 |     202 | 71.7ms |    53% |
|     600 |     199 | 71.7ms |  67.2% |
|     900 |     200 | 77.3ms |  77.9% |
|    1200 |     200 | 80.5ms |  83.3% |

<Card title="Open this example" icon="play" href="https://breakscale.tech">
  Load **Rate limited API** from the Examples menu and drag the traffic slider yourself.
</Card>