Rate Limiting

The API enforces rate limits to ensure fair usage and service stability. Limits are applied per API key — your sandbox and production keys each have their own budget.

Current limits

Higher production throughput can be granted on request — contact the Call+ team with your expected volume and tenant id.

Rate limit headers

Every authenticated response includes these headers:

When a rate limit is exceeded, the response also includes:

Handling a 429 response

When you exceed the limit, the API returns (sandbox example — production is identical with its 60-request limit):

HTTP 429
Retry-After: 17
X-RateLimit-Limit: 40
X-RateLimit-Remaining: 0
X-RateLimit-Reset: 1786356017

{
  "success": false,
  "requestId": "...",
  "error": {
    "code": "RATE_LIMIT_EXCEEDED",
    "message": "Too many requests. Limit: 40 requests per minute."
  }
}

Recommended retry strategy

1. Read the Retry-After header value.
2. Wait for the specified number of seconds.
3. Retry the request.

For automated integrations, implement exponential backoff as a fallback:

wait = min(2^attempt * 1 second, 60 seconds)

Tips

• Batch your work — run simulations sequentially rather than in parallel bursts.
• Cache results — simulation results don't change. Store the simulationId and retrieve results with GET /simulations/{simulationId}/pdf instead of re-running the simulation.
• Use sourceReferenceId — sending the same sourceReferenceId returns the previously persisted simulation instead of running a new one. Note the request itself still counts toward your rate limit budget.
• Monitor the headers — check X-RateLimit-Remaining proactively to avoid hitting the limit.