If there is something I've learned from AWS outages (they tend to publish detailed post-mortem), no matter how you design your architecture in a distribute way you will always have Single Point of Failure (SPOF) and sometimes discover SPOF you didn't think of.
Sometimes it's a script responsible of deployment that will propagate an issue to the whole system. Sometimes it's the routing that will go wrong (for example when AWS routed all production traffic to the test cluster instead of production cluster).
Sometimes it's a script responsible of deployment that will propagate an issue to the whole system. Sometimes it's the routing that will go wrong (for example when AWS routed all production traffic to the test cluster instead of production cluster).