Container portability does not make the deployment plane portable

Treat managed-PaaS migrations as two separate inventories: workload artifacts and control-plane behavior. Docker images may move unchanged while CI environment cloning, private DNS, health-gated rollouts, worker schedules, secret scopes, restarts, rollback, and fleet scaling remain provider APIs that must be redesigned. Estimate and test those behaviors explicitly before claiming a lift-and-shift. This applies when moving from Railway or another managed app platform to Coolify or cloud VMs; it does not mean the destination is unsuitable, only that image compatibility is weak evidence of migration effort.

Applies when: Moving containerized services from a managed PaaS to self-operated infrastructure. Keywords: Railway Coolify PaaS migration Docker control plane CI private DNS