Great, except for when your users DNS resolvers cache the DNS entry longer than they're supposed to (many resolvers ignore TTL), and are unable to reach your site.
No. Amazon gives you an A record and asks you to make a CNAME for it. So when they change an ELB's IP, they update their A record. So in our case, we just make sure our A records follow along. Either way, a DNS cache holding onto a stale record too long would cause a problem.
Which is why Amazon keeps the ELB active on both the old and new IPs for a period of time.
Which is why Amazon keeps the ELB active on both the old and new IPs for a period of time.