Dealing with a DNS cache is probably the largest challenge of a DNS failover service. Even when setting the TTL for your ‘A’ record to a very low number, certain ISPs or networks just like to ignore those TTLs and elect to set the cache for a value that they deem appropriate. AOL is a prime example. If you set your TTL to 60 seconds, AOL thinks it is too low and automatically adjusts it up to 15 minutes (at least the last time we checked). What can you do about this? Usually not much. If your application can’t handle any cache, then you may wish to consider our Instant Failover a.k.a. Cloud Load Balancing solution which eliminates this problem completely. Otherwise, you simply have to wait it out. The good news is that this really only affects a very small portion of the Internet at large. I’d say that at the most, maybe 2-5% of users who have previously cached your IP will encounter an issue after an ‘A’ record failover, so for the price, it still does a fantastic job.