# Welcome to nthbouncer

## Introduction

nthbouncer is a concurrency governor for APIs with a hard shared limit.
It sits in front of origins you operate or third-party APIs that enforce a hard
concurrency or rate limit. Each **pool** admits up to N in-flight requests
across every caller and never over-runs the limit you configure (or that
adaptive mode discovers from upstream `429`s).

You manage pools, keys, credentials, and billing in the dashboard at
[nthbouncer.com](https://nthbouncer.com). Clients call your pool hostname on
`*.nthpool.cloud` (or a custom domain), or take a
[concurrency lock](/docs/api/locks) and call the origin themselves.

nthbouncer is not an API gateway and not an LLM gateway. Proxy when you want
nthbouncer to call upstream. Use locks when you front a public endpoint or keep
the origin client in your process. For SaaS origins with account-level
concurrency limits, see the [knowledge base](/docs/knowledge-base).

## How it fits together

1. Create a **pool** and point it at one or more allowed origins.
2. Choose **managed** custody (nthbouncer holds and signs upstream credentials)
   or **pass-through** (your client sends upstream auth; nthbouncer relays it).
3. Mint a **pool key** and call `https://‹pool›.nthpool.cloud/...` with that key.
4. Tune concurrency, queue depth, RPM, retries, and optional response cache on
   the pool's Concurrency settings.
5. When several pools share one origin concurrency limit, put them on a
   [Capacity](/docs/capacity) budget. Fixed caps each pool at its allocation.
   Auto keeps reserved pins local and moves float toward load.
6. Use the pool's [Metrics](/docs/pools/metrics) tab for admit/queue/reject proof.
   [Billing](/docs/billing) remains the place for request allowance.

## Next steps

- [Quickstart](/docs/quickstart)
- [Pools](/docs/pools)
- [Capacity](/docs/capacity)
- [Agents](/docs/agents)
- [Metrics](/docs/pools/metrics)
- [Concurrency locks API](/docs/api/locks)
- [Credentials](/docs/credentials) · [Domains](/docs/domains) · [IP Policies](/docs/ip-policies)
- [Knowledge base](/docs/knowledge-base)