First of all, immutable infrastructure makes the concept of configuration drift obsolete. There is no configuration management so there can also be no drift. The upgrade is much safer as well because we cannot end up in a half-baked state. That is the state that's neither the previous version nor the next version, but something in between. The deployment process provides binary information: either the machine is created and operational or it isn't. There's no other way.
For immutable infrastructure to work without affecting uptime, you also need the following:
- Load balancing
- Some degree of redundancy
After all, the upgrade process consists of taking down an entire instance. You cannot rely on this machine's address or anything that's particular to that one machine. Instead, you need to have at least a second one that will handle the workload while you replace the other one with the more recent version. When you finish...
