Moving Live Work Without a Gap

Two ways to change a live system with less risk than a plain stop and start. A new version can run beside the old one so the change is one move and the return is one move, and a small set of workers can be kept warm so a burst never waits for a cold start. This course covers bringing a second version up beside the running one, holding a warm pool, hedging a slow call without doubling every call, and putting a bound on the age of a stored answer.