Rate Limits

Each key has its own rate, set by Nomos: 600 requests a minute unless agreed otherwise. The bucket holds a tenth of a minute’s worth, so you can burst, then settle to the rate.

Limit	Default
Requests a minute	600
Burst	60 (a tenth of a minute’s worth, at least 10)
Requests in flight at once	4
Streams open at once	2

Every answer carries x-ratelimit-limit (your rate a minute) and x-ratelimit-remaining (what is left in the bucket). Past the rate, or past 4 requests at once, the API answers 429 with a Retry-After header in seconds. Wait that long and retry. A 503 means a part of the index is not ready yet (a restart, a feature being switched on): retry after a few seconds with backoff. Treat a 500 the same way, a few times at most. Pages are big on purpose (up to 1,000 trades, 50,000 fills), so a well-built client rarely needs the full rate. Ask Nomos if you need more.

A Client That Waits and Retries

import os, time, requests

session = requests.Session()
session.headers["Authorization"] = f"Bearer {os.environ['CODEX_KEY']}"
BASE = "https://codex-api.nomos.trade"

def get(path, **params):
    for attempt in range(6):
        r = session.get(BASE + path, params=params, timeout=30)
        if r.status_code == 429:
            time.sleep(int(r.headers.get("Retry-After", "1")))
            continue
        if r.status_code in (500, 503):
            time.sleep(min(2 ** attempt, 30))
            continue
        r.raise_for_status()
        return r.json()
    r.raise_for_status()

const BASE = "https://codex-api.nomos.trade";
const headers = { Authorization: `Bearer ${process.env.CODEX_KEY}` };
const sleep = (ms) => new Promise((r) => setTimeout(r, ms));

export async function get(path, params = {}) {
  const url = BASE + path + "?" + new URLSearchParams(params);
  for (let attempt = 0; attempt < 6; attempt++) {
    const res = await fetch(url, { headers });
    if (res.status === 429) {
      await sleep(1000 * Number(res.headers.get("retry-after") ?? 1));
      continue;
    }
    if (res.status === 500 || res.status === 503) {
      await sleep(Math.min(2 ** attempt, 30) * 1000);
      continue;
    }
    if (!res.ok) throw new Error((await res.json()).error);
    return res.json();
  }
  throw new Error("gave up after 6 tries");
}

The recipes in these docs use this get().

Getting Started

Concepts

Recipes

A Client That Waits and Retries

​A Client That Waits and Retries

A Client That Waits and Retries