Dumb question but what's the difference between the two? If the underlying config is broken then DNS resolution would fail, and that's basically the only way resolution fails, no?
My speculation: 1st one - it just DNS fails and you can repeat later. second one - you need working DNS to update your DNS servers with new configuration endpoints where DynamoDB fetches its config (classical case of circular dependencies - i even managed get similar problem with two small dns servers...)
DNS is trivial to distribute if your backing storage is accessible and/or local to each resolver, so it's a reasonable distinction to make: It suggests someone has preferred consistency at a level where DNS doesn't really provide consistency (due to caching in resolvers along the path) anyway, over a system with fewer failure points.
I feel like even Amazon/AWS wouldn't be that dim, they surely have professionals who know how to build somewhat resilient distributed systems when DNS is involved :)
I doubt a circular dependency is the cause here (probably something even more basic). That being said, I could absolutely see how a circular dependency could accidentally creep in, especially as systems evolve over time.
Systems often start with minimal dependencies, and then over time you add a dependency on X for a limited use case as a convenience. Then over time, since it's already being used it gets added to other use cases until you eventually find out that it's a critical dependency.
