EventBridge to Lambda concurrency limits on Genesys interaction events

Spiking to 1000 concurrent Lambdas during peak hours. EventBridge sends Genesys interaction events. My handler is simple JSON parse and S3 put. Still hitting throttles.

  • Lambda: Node 18, 512MB, 10s timeout
  • Provisioned Concurrency: 500
  • EventBridge Rule: 1000 max batch size

Checked CloudWatch. No errors in the function logs. Just throttled invocations. What am I missing?