“Rollouts are an example of the need to think about orchestration, service discovery and load balancing in a holistic way. If we have a service with N instances, and we turn down and replace all of them with N other instances in a very short period of time — of the order of seconds, rather than minutes — then in many cases, our systems will have problems, even if the new instances are ready and able to serve traffic.”
https://www.stanza.systems/post/why-health-checks-are-like-sidewalks