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Rate limits protect the API for everyone. Limits are applied per API key.

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Default limits

Endpoint groupLimit
POST /messages100 requests/second, burst 300
All other endpoints25 requests/second, burst 75
Limits scale automatically as your sending volume grows. If you’re hitting limits during normal operation, contact us — we’ll usually raise them before you ask.

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Response headers

Every response includes your current limit status: 
X-RateLimit-Limit: 100
X-RateLimit-Remaining: 87
X-RateLimit-Reset: 1718721600
HeaderDescription
X-RateLimit-LimitRequests allowed in the current window
X-RateLimit-RemainingRequests left in the current window
X-RateLimit-ResetUnix timestamp when the window resets

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When you exceed a limit

You’ll receive a 429 with a rate_limit_error and a Retry-After header (seconds to wait): 
{
  "error": {
    "type": "rate_limit_error",
    "code": "rate_limit_exceeded",
    "message": "Rate limit exceeded, retry after 2 seconds",
    "param": null
  }
}

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Handling rate limits

Back off and retry rather than failing the request outright: 
async function sendWithRetry(payload, attempt = 0) {
  try {
    return await pulsewave.messages.send(payload);
  } catch (err) {
    if (err.type === 'rate_limit_error' && attempt < 5) {
      const delay = Number(err.retryAfter ?? 1) * 1000;
      await new Promise((r) => setTimeout(r, delay));
      return sendWithRetry(payload, attempt + 1);
    }
    throw err;
  }
}
Official SDKs implement this backoff automatically.