It's awfully similar to a lane of PCIe 4.0, if we're talking about instance storage. It reads like they've chosen to map each physical device to a single PCIe lane. Surely the AWS Nitro hardware platform has longer cycle times than PCIe. Note that once the instance type has multiple block devices exposed (i.e. im4gn.8xlarge or higher), striping across these will reach higher throughput (2 devices yields 4G/s, 4 yields 8G/s).