I'm pondering Outputs and mutual dependancy. Let's say I want to make 2 AWS security groups each of which wants to be confgured in the other's Ingress/Egress rules. e,g, Public needs Egress on port 8080 to Private and Private needs Ingress from Public on 8080. Is it possible to code this in pulumi? I would do it by hand by making the two groups and then adding the rules when I knew the names, but is that possible in pulumi?

yep, totally possible. you define the two groups, then use this resource to add the rules: https://www.pulumi.com/docs/reference/pkg/aws/ec2/securitygrouprule/

Awesome thanks