> 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 & Connection Limits

The gateway budgets your traffic with a token-bucket limiter, plus a per-IP request limit and WebSocket connection and subscription caps. Limits are tiered to support both general programmatic use and high-throughput market-making.

**The budget is weight per second, not requests per second.** Most requests cost one unit, heavy aggregate and history reads cost five, and a batch submit scales with its size — so a Pro caller at 20/s gets 20 ticker reads per second but only 4 `/fills` reads. The full model, including the three independent budgets, the response headers, and the current per-tier ceilings, is documented once in [**Rate Limits**](/interfaces/rate-limits.md) under Interfaces. Read that page before building a client-side limiter; the per-operation costs are normative in the OpenAPI spec at `/openapi.json`.

When you exceed a limit the gateway returns **HTTP 429** with `retry-after`. `x-ratelimit-limit` and `x-ratelimit-remaining` accompany every authenticated response so you can pace without tripping the limiter; `x-ratelimit-reset` and `retry-after` appear on the 429 only.

### 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) |

> **Status:** testnet preview. Tier ceilings are current configuration 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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