TTLs are an integral part of DNS. They can directly impact on the amount of query volume that is attributable to your authoritative service. In cases where you need to make changes to a record quickly, a too-long TTL can result in longer-than-expected change in propagation to all users.
When setting the TTL, here are some best practices and points of consideration:
For records that leverage an advanced traffic management configuration—such as NS1’s Filter Chain—it’s best to keep the TTL as short as possible.* As such, when a change is enacted by the system, users on the other end requesting the name are given the most recent information.*Note: Most recursive servers do not understand a TTL shorter than 30 seconds. If you set your TTL to a number lower than 30 seconds, results are likely not to be favorable in the long run.
For records that rarely change—such as TXT or MX records—it’s best to keep the TTL somewhere between an hour (3600s) and a day (86400s). When there is a need to enact changes impacting these types of records, we recommend reducing the TTL before enacting any changes to ensure that the changes are propagated quickly.
For help with random label traffic (which logs against your base domain), you can edit the NX TTL value to a higher value, causing resolvers to not re-request that same domain again for longer. If your active domains do not have answers changed frequently either, it would also help to increase their TTL value as well.