A global service uses DNS-based failover and requires fast client reaction to endpoint changes. What DNS TTL strategy balances quick failover with realistic operational cost?

A low TTL (Time To Live), such as 30-60 seconds, is the most effective strategy for fast DNS-based failover. This ensures that when an endpoint changes, client resolvers quickly expire their cached DNS records and query for the updated information, leading to rapid redirection to healthy endpoints. The trade-off is an increased query load on authoritative nameservers, but this is generally manageable for critical services and is a necessary cost for quick failover. Setting a very large TTL would cause clients to cache old records for extended periods, delaying failover significantly. Enabling DNSSEC primarily provides security and data integrity; it does not inherently force faster re-validation or accelerate failover. Removing all TTL values is not a valid DNS configuration; a TTL must always be specified, and even if it were possible, it would lead to an unmanageable and unnecessary query storm.