Webhook Delivery API 429 errors during JMeter load test

Looking for some advice on troubleshooting this rate limiting issue we are seeing during our latest load testing cycle. We are validating the throughput capacity for our outbound notification service using JMeter 5.6 against the Genesys Cloud US1 environment.

When we ramp up the thread count to 50 concurrent users hitting POST /api/v2/integrations/webhooks/delivery, the system immediately returns 429 Too Many Requests errors. This happens even though our average request rate is only around 15 requests per second, which seems well within standard limits based on documentation.

The error response includes a Retry-After header set to 30 seconds. We have verified that our authentication tokens are valid and not expiring mid-test. The issue appears to be consistent across different time windows in the EST timezone.

Is there a specific rate limit configuration for webhook delivery endpoints that we are missing? Or could this be related to how the API calculates concurrent connections versus total requests per second? We need to understand the bottleneck before we can proceed with our capacity planning for the new deployment. Any insights into the expected throughput for this endpoint would be appreciated.

Thanks for the help.