By default, EventBridge includes retry mechanisms for delivery failures, particularly when targets like Lambda functions or Step Functions fail to process an event. However, if these retry policies are disabled or misconfigured, EventBridge may treat failed deliveries as successful, prompting upstream services to republish the same event multiple times in response to undelivered outcomes. This leads to: * Duplicate event publishing and delivery * Unnecessary compute triggered by repeated events * Increased EventBridge, downstream service, and data transfer costs This behavior is especially problematic in systems where idempotency is not strictly enforced and retries are managed externally by upstream services.
EventBridge charges are based on the number of events published to an event bus, including retries or duplicate events. Each event published — whether successful or redundant — incurs cost.
