Problem
A small cloud instance already hosted another early product. Reuse reduced cost, but a collision in ports, container names, networks, volumes, environment values, or proxy rules could take the existing product down.
Approach
Existing services and resources were baselined first. The new app received an isolated Compose project, network, directory, secrets, and health check; the proxy gained only an exact host rule. After deployment, the new domain, TLS, service health, and old-service response were verified together.
Result
Release evidence covered both the new service and its neighbors, with a rollback target fixed before change. The case documents the reusable method without exposing addresses, keys, customer data, or internal topology.