EBS is slow. No way we would use it for swap. Gotta be instance storage device. And yes, we can rebuild a node from source data, we do so regularly to release changes anyways.

I figured that you were using instance attached NVMe's since you mentioned the scale of your load – an EBS even with the io2 Express storage class can't keep up with a physical NVMe drive on high intensity I/O tasks.

Regardless, AWS takes care the hardware cycling / migration in either case.