When you have created a DNS Failover pool and have assigned it to an ‘A’ or ‘AAAA’ record, you want the flexibility to switch back and forth between the available servers during outages. To best accomplish this, we highly recommend decreasing the TTL value for that particular DNS record to the lowest allowable setting of 60 seconds. It is true that this will increase your query count for high-traffic records (e.g. your www record) but you must weigh flexibility against query cost to determine which is most important. If query cost could be high and flexibility is not as important, consider increasing the TTL to something higher. Determining the actual value is best left to you!
NOTE: In the current version of the Cloud Management portal, when you select a Failover Pool for an A or AAAA record, we automatically update the TTL to 60 seconds because this is the most desirable configuration based on our experience. ISPs tend to obey this setting the most, and as such, we configure it by default for you.