Autoscaling groups with ansible-pull + cloud init to configure instances as they are spun up by AWS is what I've had the most success with. So your autoscaling group spins up a new instance using a prebaked AMI, and on first boot cloud-init will run ansible-pull locally to grab the latest configs and start up services as needed. Alternatively you can just use ansible to bake a new AMI as needed and skip the ansible-pull + cloud-init part altogether.