> For the complete documentation index, see [llms.txt](https://docs.nexus.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.nexus.xyz/exchange/apis-and-rates/rate-limits.md).

# Rate-Limits

The gateway enforces per-API-key rate limits with a token-bucket limiter, plus a per-IP request limit and a WebSocket connection cap. Limits are tiered to support both general programmatic use and high-throughput market-making.

### Request rate (per API key)

| Tier         | Request limit | WebSocket connections | Assignment           |
| ------------ | ------------- | --------------------- | -------------------- |
| Pro          | 20 req/s      | 5                     | Default for all keys |
| Market Maker | 2,000 req/s   | 100                   | Admin-assigned       |

A per-IP limit of **50 req/s** applies in addition to the per-key limit.

When you exceed your limit, the gateway returns **HTTP 429** with a `Retry-After` header. Every response also carries `X-RateLimit-*` headers reporting your tier's ceiling and current usage, so you can pace clients without tripping the limiter.

### WebSocket connections

* **Pro keys: up to 5** active WebSocket connections; **Market Maker: up to 100**.
* Connections beyond the cap are rejected.

### Other limits

| Limit                      | Value                          |
| -------------------------- | ------------------------------ |
| HMAC timestamp window      | ±30s of server time            |
| WebSocket token lifetime   | 60s, single-use                |
| Session token lifetime     | 24h                            |
| Faucet (`/account/credit`) | 500 USDX/day per key (testnet) |

### Designing for the limits

* Batch order placement with `POST /orders/batch` instead of issuing many single `POST /orders` calls.
* Prefer WebSocket streams over REST polling for order book and trade data — it is both faster and far cheaper against your rate budget.
* Cache market metadata (`GET /markets`) rather than re-fetching it on every cycle.
* Pace from the `X-RateLimit-*` headers rather than retrying blindly after a 429.

> **Status:** testnet preview. Tier ceilings are configurable and may change as the tier system is finalized across release gates. Rate-limit state is currently in-memory at the gateway and resets on restart.


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