We're looking at lowering our DNS A record TTL to around 1 minute, to enable us to quickly switch to a backup server should the main one fail (whether this is automatic, using AWS Health Checks etc, or manual, is largely irrelevant to this question).
I'm aware this will put a significantly higher load on the DNS server, but this isn't an issue.
What I'm concerned about it how the total site load time will be increased, because of the additional overhead of having to look up the DNS records with a lot more requests.
How to I balance these issues?
I'm obviously disregarding factors outside my control, such as ISP DNS caching.