Regarding the VPC part of the question, yes. The replacement spot instance will get the same VPC/Subnet/AZ and all the relevant settings from the instance it's

Regarding the VPC part of the question, yes. The replacement spot instance will get the same VPC/Subnet/AZ and all the relevant settings from the instance it's supposed to replace. Regarding the AMI/post-instal part of the question, this is already covered by AutoScaling. Remember, it works against AutoScaling groups, where all instances start with the same AMI and runan userdata script at boot. All this is preserved for the spot instances.