No idea why this is happening, SIP 503 Service Unavailable appears when concurrent calls exceed 50. The environment is US-East. JMeter script uses 100 threads with 5-second ramp-up. Calls work fine at low volume. Is this a default WebSocket connection limit or API rate limit? Need to know if this is a config issue or infrastructure cap for planning.
If I remember correctly, SIP 503 errors during load testing usually indicate that the underlying media resources or trunk capacity in Genesys Cloud has been exhausted, rather than a simple API rate limit hitting the WebSocket layer. The US-East region has specific concurrent session thresholds that are distinct from API call limits, and exceeding the allocated media server capacity for your org will trigger this service unavailable response immediately. You should verify the current concurrent call allocation in the Admin console under Telephony > Trunks to ensure the load test volume does not exceed the licensed media resource pool for that specific edge location.
GET https://{{org_id}}.mygen.com/api/v2/trunks
Header: Authorization: Bearer {{access_token}}
Filter: status == "active" && edgeLocation == "us-east-1"
Checking the trunk status and concurrent call limits via the REST API provides the exact ceiling for your load test configuration before increasing thread counts further.