DNS record changes propagate in less than a minute, but
TTL times will impact on how quickly
DNS resolvers check back for updated records.
Q. How quickly will changes I make to my DNS settings on Amazon Route 53 propagate globally?
Amazon Route 53 is designed to propagate updates you make to your DNS records to its world-wide network of authoritative DNS servers within 60 seconds under normal conditions. A change is successfully propagated world-wide when the API call returns an INSYNC status listing.
Note that caching DNS resolvers are outside the control of the Amazon Route 53 service and will cache your resource record sets according to their time to live (TTL). The INSYNC or PENDING status of a change refers only to the state of Route 53’s authoritative DNS servers.
Or, if you prefer the AWS developer forums...
You can expect it to have propagated to all Route 53 servers around the world within a minute. However, keep in mind that the TTL determines how quickly the clients will see the updated information. If you set the TTL for a record to say 3600 seconds, DNS resolvers can cache that data for up to an hour before going back to Route 53 again. If it is important to make the updated record propagate down to the end users as fast as possible, I would recommend a TTL of 60 seconds.
As the TTL is configured for each record, you can use different values. If you don't plan to make any changes to a record in the near future, a higher TTL can help you save on query costs and make things a bit more efficient. As an example, you might not need to update your MX records just like that. Let's say you have a TTL set to 43200 seconds (12 hours) for your MX records. If you ever switch to another e-mail provider, simply lower the TTL in advance. As soon as the original TTL has expired, you can proceed with the move. The updated records will now propagate much faster thanks to the lower TTL. Change the TTL back to the original value at the same time.