AWS Route 53 TTL (Time To Live) is the amount of time that a response to a Route 53 request will be good for. So the local client machine may cache that response and be assured that the corresponding data is good for the equivalent time period. Specifying the TTL is a balance between reducing the number of requests that the Route 53 service receives and ensuring that the cache data on the remote machines is updated with any changes. Having a high TTL of 24 hours reduces the flexibility of changes you can make to your systems, while having a low TTL of 30 seconds will increase the number of Route 53 hits subsequently increasing your costs. All Route 53 records require you to define a TTL, except Alias records.