Rate limits

const sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms));

export async function requestWithRetry(url, init = {}, { maxAttempts = 5, baseMs = 500, capMs = 60_000 } = {}) {
  for (let attempt = 0; ; attempt++) {
    let res;
    try {
      res = await fetch(url, init);
    } catch (error) {
      if (attempt + 1 >= maxAttempts) throw error;
      await sleep(Math.random() * Math.min(capMs, baseMs * 2 ** attempt));
      continue;
    }

    if (res.status === 429 && attempt + 1 < maxAttempts) {
      // Respect the server: Retry-After is in seconds.
      const retryAfter = Number(res.headers.get("retry-after") ?? 1);
      await sleep(retryAfter * 1000 + Math.random() * 250);
      continue;
    }
    if (res.status >= 500 && attempt + 1 < maxAttempts) {
      // Full jitter: a random wait between 0 and the exponential cap.
      await sleep(Math.random() * Math.min(capMs, baseMs * 2 ** attempt));
      continue;
    }
    return res;
  }
}

const res = await requestWithRetry(
  `https://simplecold.com/api/v1/api-validation/single?email=${encodeURIComponent("[email protected]")}`,
  { headers: { Authorization: `Bearer ${process.env.SIMPLECOLD_API_KEY}` } },
);
console.log(res.status, res.headers.get("ratelimit-remaining"), await res.json());

import os
import random
import time

import requests

API = "https://simplecold.com/api/v1"
session = requests.Session()
session.headers["Authorization"] = f"Bearer {os.environ['SIMPLECOLD_API_KEY']}"

def request_with_retry(method, url, max_attempts=5, base=0.5, cap=60, **kwargs):
    for attempt in range(max_attempts):
        last = attempt + 1 >= max_attempts
        try:
            res = session.request(method, url, timeout=30, **kwargs)
        except requests.RequestException:
            if last:
                raise
            time.sleep(random.uniform(0, min(cap, base * 2**attempt)))
            continue

        if res.status_code == 429 and not last:
            # Respect the server: Retry-After is in seconds.
            time.sleep(int(res.headers.get("Retry-After", 1)) + random.uniform(0, 0.25))
            continue
        if res.status_code >= 500 and not last:
            # Full jitter: a random wait between 0 and the exponential cap.
            time.sleep(random.uniform(0, min(cap, base * 2**attempt)))
            continue
        return res

res = request_with_retry("GET", f"{API}/api-validation/single", params={"email": "[email protected]"})
print(res.status_code, res.headers.get("RateLimit-Remaining"), res.json())

<?php
const API = 'https://simplecold.com/api/v1';

function request_with_retry(string $url, int $maxAttempts = 5, float $base = 0.5, float $cap = 60): array
{
    for ($attempt = 0; ; $attempt++) {
        $last = $attempt + 1 >= $maxAttempts;
        $headers = [];
        $ch = curl_init($url);
        curl_setopt_array($ch, [
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_HTTPHEADER => ['Authorization: Bearer ' . getenv('SIMPLECOLD_API_KEY')],
            CURLOPT_TIMEOUT => 30,
            CURLOPT_HEADERFUNCTION => function ($ch, $line) use (&$headers) {
                $parts = explode(':', $line, 2);
                if (count($parts) === 2) {
                    $headers[strtolower(trim($parts[0]))] = trim($parts[1]);
                }
                return strlen($line);
            },
        ]);
        $body = curl_exec($ch);
        $status = curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
        // Full jitter: a random wait between 0 and the exponential cap.
        $backoff = mt_rand() / mt_getrandmax() * min($cap, $base * 2 ** $attempt);

        if ($body === false) {
            if ($last) {
                throw new RuntimeException(curl_error($ch));
            }
            usleep((int) ($backoff * 1e6));
            continue;
        }
        if ($status === 429 && !$last) {
            // Respect the server: Retry-After is in seconds.
            usleep((int) ($headers['retry-after'] ?? 1) * 1_000_000 + mt_rand(0, 250_000));
            continue;
        }
        if ($status >= 500 && !$last) {
            usleep((int) ($backoff * 1e6));
            continue;
        }
        return ['status' => $status, 'headers' => $headers, 'body' => json_decode($body, true)];
    }
}

$res = request_with_retry(API . '/api-validation/single?' . http_build_query(['email' => '[email protected]']));
echo $res['status'], ' ', $res['headers']['ratelimit-remaining'] ?? '-', PHP_EOL;