Move external traffic progressively at 15, 20, 25% to mw on k8s.
Info from T351074: Move servers from the appserver/api cluster to kubernetes:
For every 5% of external traffic we move, we've needed to bump mw-web by 12-13 replicas and mw-api-ext by 10 replicas.
This means that for every 5% increase in traffic, we're requiring 22-23 additional replicas. Given every pod requires 5.6 CPUs it means we're going to need about 123 cores per traffic bump, or roughly 3 servers as our servers have 48 cores each.
The above calculation is per-datacenter, of course.