Internal and external apps are both deployed on the same PaaS. Only difference is that internal apps aren't reachable "outside the VPN"; when it comes to building your service, it's an extra line of yaml in your service config. There's a network engineering team who works with the PaaS team to make that happen - it's definitely a nice luxury of a big company that you don't need to worry about setting up VPCs etc yourself.

The actual PaaS relies pretty heavily on AWS Cloud Formation - it predates swarm, mesosphere, kube, etc. So when we deploy a new version of a service, it's really "deploy an auto scaling group of EC2 instances across several AZs fronted by an ELB, then there's an automatic DNS change made which makes the new stack of EC2 instances live once the new stack is validated as working". The upside of the one service per EC2 image approach is no multi-tenancy interference - downsides are cost and it takes a bit longer to deploy. There's a project underway to switch compute to being Kube-based though, so that's promising.

All this is apples and oranges though - solns for big companies don't make sense for a 1-person shop. I still have side projects being deployed via ansible and git pull instead of Docker, because it hasn't been worth the ROI to upgrade to the latter.

Re asparck - yeah, it was my personal site but I struggled to find the time to work on it. In the end I decided it was better to have it offline than terribly out of date, but hopefully I'll resurrect it some day.