Screen Recording API 503 during JMeter load test

Just noticed that the Screen Recording API returns 503 Service Unavailable when simulating high concurrency in JMeter.

Environment: Genesys Cloud US1
Tool: JMeter 5.6
Endpoint: /api/v2/recordings/screen
Auth: Bearer token

Config: 50 concurrent threads attempt to initiate screen recording sessions every 5 seconds. The first 20 requests succeed, but subsequent requests fail with 503. Error response body shows: {"status":503,"timestamp":"2024-05-20T14:32:11.123Z","message":"Service Unavailable"}.

This is not a standard rate limit (429). The load pattern mimics peak agent activity where multiple supervisors request screen recordings simultaneously. Is there a known connection limit for screen recording initiation in Genesys Cloud? Or does the API require specific headers for high-throughput scenarios?

Current JMeter config uses HTTP Request sampler with Keep-Alive enabled. No custom headers beyond Authorization and Content-Type: application/json. The issue persists across multiple test runs. Looking for guidance on capacity planning for screen recording endpoints under load. Any insights on expected throughput limits would be helpful.