I wonder the same, though the engineering under the hood is more interesting than I thought: http://perspectives.mvdirona.com/2015/12/vpc-nat-gateways-transact

I wonder the same, though the engineering under the hood is more interesting than I thought: http://perspectives.mvdirona.com/2015/12/vpc-nat-gateways-transactional-uniqueness-at-scale/ http://perspectives.mvdirona.com/2015/12/vpc-nat-gateways-tr... > The connections are managed by a fault-tolerant co-operation of devices in the VPC network fabric. Each new connection is assigned a port in a robust and transactional way, while also being replicated across an extensible set of multiple devices. In other words: the NAT gateway is internally horizontally scalable and resilient. Maybe it just wasn't a priority.