You can keep both the new and old process running concurrently as long as you like, and they'll both be responding to requests. You can run your health checks a

You can keep both the new and old process running concurrently as long as you like, and they'll both be responding to requests. You can run your health checks at this time (perhaps distinguishing the process with a header). When you're confident, send a signal to the old process to gracefully exit.