EventBridge batch size causing Lambda concurrency spikes

  • Genesys Cloud v2
  • AWS Lambda (Node.js 18)
  • Slack Bolt 4

Could someone explain why my EventBridge trigger is bursting concurrency? I am processing routing.interaction.created events. The batch size is 10, but GC sends 1000 events in parallel. My handler throws ConditionalCheckFailedException on Slack message ID uniqueness. I need to dedup before writing to Slack. Is there a GC webhook header I can use to throttle or batch these client-side?