One managed service in your primary region is having a bad day and your product is down with it. What can you do during the outage, and what should you have designed before it?
During the event your only levers are the ones already built: fail over, serve degraded from cache, or shed the dependent feature. Beforehand the work is finding your transitive dependencies on foundational services, making the running system statically stable, and choosing which features are allowed to fail alone.