TTL stands for Time to Live and is a field on DNS records that controls how long each record is valid and how long it takes for record updates to reach end-users. DNS TTL is expressed in terms of time because it determines the amount of time before the resolver gathers the details of a website. The TTL is like a stopwatch for how long to keep a DNS record. Longer TTLs speed up DNS lookups by increasing the chance of cached results, but a longer TTL also means that updates to your records take longer to go into effect. DNS TTL is a setting that tells the DNS resolver how long to cache a query before requesting a new one. The information gathered is then stored in the cache of the recursive or local resolver’s cache that handles the TTL until it has to collect new details.

DNS TTL is particularly useful for websites that constantly and frequently change their web content. With a lower TTL, a website can receive the most recent updates more often. Shorter TTLs can cause heavier loads on an authoritative nameserver, but can be useful when changing the address of critical services like Web servers or MX records, and therefore are often lowered by the DNS administrator prior to a service being moved, in order to minimize disruptions. It is essential to understand how you are implementing your TTL. You want it to be the perfect balance between “quickly updating” and “resource savvy.” Straying too far in either direction it will cost you both time and resources to accommodate.