Best practices - Crustdata Docs

Practical patterns for building reliable clients against the Crustdata API. Each section explains the signal the API sends, then shows the code you need to react to it.

Handle rate limits

Crustdata returns rate limit headers on every response. Read them after each call and pace your client accordingly — this is more reliable than guessing limits up front, and it gives you visibility before you hit the cap.

Rate limits are enforced on a sliding window. The window does not reset at fixed clock intervals — instead, each request counts against the limit for the duration of the window, and x-ratelimit-reset tells you how many seconds until the oldest request ages out and capacity frees up. Spreading traffic evenly is safer than bursting and waiting for a “reset.”

Rate limit headers

Header	Meaning
`x-ratelimit-limit`	Maximum requests allowed within the sliding window.
`x-ratelimit-remaining`	Requests you have left right now.
`x-ratelimit-reset`	Seconds until the next request ages out and capacity frees up.

Example values on a response:

x-ratelimit-limit: 30
x-ratelimit-remaining: 29
x-ratelimit-reset: 60

Read the headers and pace requests

After each request, inspect x-ratelimit-remaining. When it gets close to zero, wait x-ratelimit-reset seconds before sending the next call.

import time
import requests

def call_crustdata(url, payload, api_key):
    response = requests.post(
        url,
        headers={
            "authorization": f"Bearer {api_key}",
            "content-type": "application/json",
            "x-api-version": "2025-11-01",
        },
        json=payload,
    )

    remaining = int(response.headers.get("x-ratelimit-remaining", 1))
    reset = int(response.headers.get("x-ratelimit-reset", 0))

    if remaining <= 1 and reset > 0:
        time.sleep(reset)

    response.raise_for_status()
    return response.json()

async function callCrustdata(url, payload, apiKey) {
    const response = await fetch(url, {
        method: "POST",
        headers: {
            authorization: `Bearer ${apiKey}`,
            "content-type": "application/json",
            "x-api-version": "2025-11-01",
        },
        body: JSON.stringify(payload),
    });

    const remaining = Number(
        response.headers.get("x-ratelimit-remaining") ?? 1,
    );
    const reset = Number(response.headers.get("x-ratelimit-reset") ?? 0);

    if (remaining <= 1 && reset > 0) {
        await new Promise((r) => setTimeout(r, reset * 1000));
    }

    if (!response.ok) {
        throw new Error(`Request failed: ${response.status}`);
    }
    return response.json();
}

Retry on 429 with backoff and jitter

If you do receive a 429 Too Many Requests, wait x-ratelimit-reset seconds and retry. Add jitter so concurrent workers do not all retry at the same instant.

import random
import time
import requests

def call_with_retry(url, payload, api_key, max_retries=3):
    headers = {
        "authorization": f"Bearer {api_key}",
        "content-type": "application/json",
        "x-api-version": "2025-11-01",
    }
    for attempt in range(max_retries):
        response = requests.post(url, headers=headers, json=payload)
        if response.status_code != 429:
            response.raise_for_status()
            return response.json()
        reset = int(response.headers.get("x-ratelimit-reset", 1))
        time.sleep(reset + random.uniform(0, 1))
    raise RuntimeError("Exceeded retry budget")

async function callWithRetry(url, payload, apiKey, maxRetries = 3) {
    const headers = {
        authorization: `Bearer ${apiKey}`,
        "content-type": "application/json",
        "x-api-version": "2025-11-01",
    };
    for (let attempt = 0; attempt < maxRetries; attempt++) {
        const response = await fetch(url, {
            method: "POST",
            headers,
            body: JSON.stringify(payload),
        });
        if (response.status !== 429) {
            if (!response.ok) {
                throw new Error(`Request failed: ${response.status}`);
            }
            return response.json();
        }
        const reset = Number(
            response.headers.get("x-ratelimit-reset") ?? 1,
        );
        const jitter = Math.random();
        await new Promise((r) => setTimeout(r, (reset + jitter) * 1000));
    }
    throw new Error("Exceeded retry budget");
}

See Rate limits for default per-endpoint limits and how to request higher throughput.

Handle insufficient credits

When your account has no remaining credits, the API returns 402 Payment Required with a structured error body. Treat this as terminal — retrying will not succeed until credits are added. An API key that has its own monthly cap returns the same status and error.type once that cap is exhausted, with a message naming the key’s limit and its reset date. Handle both with the same branch — see Per-key monthly limit.

Response shape

{
    "error": {
        "type": "insufficient_credits",
        "message": "Insufficient credits. Please get in touch with the Crustdata sales team.",
        "metadata": []
    }
}

Field	Description
`error.type`	`insufficient_credits` for this case.
`error.message`	Human-readable message safe to surface in logs and UI.
`error.metadata`	Reserved for additional context. May be empty.

Detect and stop

Catch 402 early, pause the workflow, and alert the operator. Do not feed the same request back into a retry loop.

import requests

class InsufficientCreditsError(Exception):
    pass

def call_crustdata(url, payload, api_key):
    response = requests.post(
        url,
        headers={
            "authorization": f"Bearer {api_key}",
            "content-type": "application/json",
            "x-api-version": "2025-11-01",
        },
        json=payload,
    )

    if response.status_code == 402:
        body = response.json()
        raise InsufficientCreditsError(body["error"]["message"])

    response.raise_for_status()
    return response.json()

class InsufficientCreditsError extends Error {}

async function callCrustdata(url, payload, apiKey) {
    const response = await fetch(url, {
        method: "POST",
        headers: {
            authorization: `Bearer ${apiKey}`,
            "content-type": "application/json",
            "x-api-version": "2025-11-01",
        },
        body: JSON.stringify(payload),
    });

    if (response.status === 402) {
        const body = await response.json();
        throw new InsufficientCreditsError(body.error.message);
    }

    if (!response.ok) {
        throw new Error(`Request failed: ${response.status}`);
    }
    return response.json();
}

Do not retry 402 responses. Repeated calls without adding credits will return the same error and obscure the real problem in your logs.

Get more credits

Reach out to support@crustdata.co to discuss your usage, upgrade your plan, or add credits to your account.

Handle denied endpoint access

A 403 Forbidden means the API key you used is not allowed to call that endpoint. A workspace admin can restrict an individual key to a subset of the endpoints the account has enabled, so a key that works for one endpoint can be refused on another.

Response shape

{
    "error": {
        "type": "permission_error",
        "message": "This API key does not have access to /person/search. A workspace admin can update the key's endpoint access in the dashboard.",
        "metadata": []
    }
}

Detect and stop

Treat 403 the way you treat 402: terminal for that endpoint, not worth retrying. Nothing you change about the request will alter the outcome. Route it to the operator, who can widen the key’s endpoint access in the dashboard.

See Permissions for the endpoint that lists what the account has enabled, and Per-key endpoint access for how a single key can be narrowed below that.

​Handle rate limits

​Rate limit headers

​Read the headers and pace requests

​Retry on 429 with backoff and jitter

​Handle insufficient credits

​Response shape

​Detect and stop

​Get more credits

​Handle denied endpoint access

​Response shape

​Detect and stop

Handle rate limits

Rate limit headers

Read the headers and pace requests

Retry on 429 with backoff and jitter

Handle insufficient credits

Response shape

Detect and stop

Get more credits

Handle denied endpoint access

Response shape

Detect and stop