Application architecture can either die perfect, or live long enough to be a huge, risky problem to solve. If you’re unlucky, that risky problem might require you to add new data boundaries in memory, persistent storage, and even in downloadable dynamic feature modules. It is possible to do it safely, though, using structured concurrency, dependency injection, and a carefully designed tenancy model. By using modern tools and proven legacy code techniques, even a big migration like this is possible without interrupting engineers with tedious migration work, or customers with forced sign outs.