Route 53: Records TTL (Time To Live)

 

In Amazon Route 53, the TTL (Time To Live) is an important DNS record setting that specifies how long (in seconds) a DNS resolver or cache should store a record before discarding it and querying the authoritative DNS server again (like Route 53) for updated information.

 Why TTL Matters important

• Caching Efficiency: Higher TTL values reduce DNS lookups by caching the result longer, improving performance and reducing load on your DNS servers.
• Flexibility and Updates: Lower TTL values make DNS changes (like failovers, IP address changes) propagate faster.

 TTL in Route 53 – Key Points

Attribute	Description
Defined per Record	TTL is set individually for each DNS record in Route 53.
Value Type	Integer, in seconds. Common values: 300, 600, 3600, etc.
Minimum TTL	No enforced minimum, but very low TTLs (e.g., <60s) may increase DNS traffic.
Effect on Caching	Shorter TTL = faster DNS propagation, but higher load.
Default Behavior	You must specify TTL when creating records (some wizards suggest 300 seconds by default).

 Example

If you create an A record like:

# text

Name:    www.web.twtechapp.com

Type:    A

Value:   172.22.33.44

TTL:     300

That means any DNS resolver that looks up www.example.com will cache the result for 5 minutes (300 seconds) before re-querying Route 53.

twtech Best Practices

• Use low TTLs (e.g., 60–300s) during:
• Website migrations
• IP changes
• Failover configuration
• Use high TTLs (e.g., 3600–86400s) for:
• Stable, rarely changing records

                * Reducing DNS costs and latency

twtech  insights:

·        To avoid querying the records  too often.

·        TTL is a value in seconds that indicates how long a DNS resolver (like twtech ISP) should cache the DNS information before refreshing it from the authoritative nameserver. 

·        This can be also be configured using the command-line tools:  like dig or nslookup. 

Project: Hands-on

How twtech creates a record set while setting value for : TTL

 Select the hosted zone to create the : A records

Create the: A records

Assign a name: springapp.twtechapp.com

Value (PubIPv address of an instance): 18.220.xxx.154

Set the  TTL to: 120 seconds

Create the A record for:  springapp.twtechapp.com

How twtech uses the UI (browser) to access the A record created:

NB:

Sometime the browsers may not be compatible with the A records: springapp.twtechapp.com

Firefox : successfully queried the application with the record set

However, google chrome won’t query data from the application using the same A record: springapp.twtechapp.com

twtech recommendation: if a browser is not compactible, try another browser.

How twtech used the cloudshell to perform nslookup for: A records

Install command utility: sudo yum install bind-utils -y

Again run the nslookup command for: springapp.twtechapp.com

#  nslookup springapp.twtechapp.com

Server:         127.0.0.11

Address:        127.0.0.11#53

Non-authoritative answer:

Name:   springapp.twtechapp.com

Address: 18.220.xxx.154

The dig command will query more data: dig springapp.twtechapp.com

twtech can also edit the A record value (PubIPv4 address) to route traffic to an instance in another region: From Ohio to N. California.

From:

To: save changes       

NB:  make sue the record set name already used in the account is not repeated

twtech needs to verify that the A record edited and directed to N. California is reachable(accessisble from the public): twetechweb.twtechapp.com

Successfully, traffic is now routed to the instance in us-west-1 (N.California) by simply:  editing an existing A records.

NB:

In order for twtech to query data from this instance, it must take: 120 sec initially set for TTL, for new data to be queried from the edited A record.

From:

To: after 120 sec Time to live (TTL)

Meaning, the records is cached for 120 secs