Data Action API 503 during high-concurrency load test

Stuck on 503 Service Unavailable when calling POST /api/v2/integrations/datapipelines/actions via JMeter 5.6.2.

Running 200 concurrent threads against Genesys Cloud BYOC Edge 24.1.0 (Asia/Singapore). The endpoint works fine at low RPS but fails immediately under load. Is there a specific rate limit for data actions that isn’t documented?