The challenge with that kind of system is flow control. Essentially everything is coupled by queues without a feedback loop. And once the system gets under load, those queues might run fuller and fuller until the whole system fails.

It’s actually similar than an in-program model where you just asynchronously queue void functions in threadpools without knowing how many actually run.

The fact that you are only running on top of managed services and that AWS can scale really well might mitigate the problem. And if you have to process all events and can not fail early or move backpressure on the initial caller there might not really be a better solution anyway. But you should be aware about it.