DNS Bytes: Tip - Best Time to Live (TTL) Settings

With so many DNS records that are used for so many different purposes, it can be hard to know what the best time to live (TTL) settings should be. That’s why for this DNS tip, we’re giving you recommendations for the most common scenarios. 

Most Common TTL Values

30 seconds TTL 

For websites or applications that provide mission-critical services, use Failover, and require a high amount of changes.

300 seconds (5 minutes) TTL Value

Best for websites that require frequent updates, but that still want to reduce resource consumption. 

1800 seconds (30 minutes) TTL Value

Ideal for websites that receive regular updates

3600 seconds (1 hour) TTL Value

Allows for caching, but is still flexible enough for fast changes when necessary.

86400 seconds (24 hours) TTL Value

Best for websites that want a daily cache utilization for faster site upload speeds.

TTL values can be set to whatever value you want, but these are the most common settings for most domains. Your specific needs and goals are what determine the value you ultimately set. Even if a record has a long TTL, you can ensure changes are seamless with careful planning. 

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Recommended TTL Settings for Common DNS Records and Configurations

Failover

The point of using Failover is to avoid downtime. With that in mind, for records using a Failover configuration, we recommend setting TTL values at 30 seconds, but no more than 300.

Load Balancing and Records Using GeoDNS

Records using advanced features like load balancing and GeoDNS should use TTL settings on the shorter side.

Mission-Critical DNS Records

Like Failover, TTL for DNS records for mission-critical applications and services should also be set to a maximum of 300 seconds, and the lower the better. 

Tip: While you can set TTL as low as 0 for a DNS record in Constellix, some resolvers may not support values under 30 seconds. If you want a TTL value that is less than 30 seconds, be sure to test the record first.

MX, DKIM, and TXT DNS Records

For mail and text records, it is recommended to use longer TTLs, ideally between 1400 and 3600 seconds.

A, CNAME, ANAME, and CDNs

For records that point to your web server, we typically recommend setting TTL at 86400 (24 hours), depending on the frequency of which your records need to be updated.

The reason TTL values are so important is that they are what dictates how long a resolver will cache your DNS record information. When you make changes to a record, the change will not be reflected at all servers globally until the TTL for the original value has expired and the server needs to make a request for the updated information.

Related Resources:

TTL Best Practices: the Long and Short of It

What is TTL