TTL

Time to Live - a value that specifies how long data should be cached or considered valid before being refreshed.

Sep 29, 2025 · About 1 min read

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TTL (Time to Live) is a value that determines how long a piece of data remains valid before it should be refreshed or discarded. In web technology, TTL appears in multiple contexts: DNS records have TTL values that control how long resolvers cache the record, HTTP cache headers use max-age to specify content freshness, and CDN configurations use TTL to determine how long edge servers cache content.

In DNS, TTL is measured in seconds and tells resolvers how long to cache a DNS response before querying the authoritative server again. A TTL of 3600 means the record is cached for one hour. Lower TTL values enable faster propagation of DNS changes but increase query load on authoritative servers. DNS administration books on Amazon explain TTL strategies.

For URL shortening services, TTL is relevant in several areas. DNS TTL affects how quickly custom domain changes propagate. CDN TTL determines how long cached redirect responses are served from edge servers. Database TTL can be used to automatically expire short URLs after a specified period.

Choosing appropriate TTL values involves balancing freshness against performance. Short TTLs ensure changes propagate quickly but increase origin server load. Long TTLs reduce server load but delay the propagation of updates. Cloud architecture books on Amazon discuss caching strategies.

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Related Terms

DNS Resolution

The process of translating a human-readable domain name into the IP address of the server hosting the website.

Link Expiration

A feature that automatically deactivates a short URL after a specified date, time, or number of clicks.

CNAME Record

A DNS record that maps one domain name to another, commonly used to point custom domains to URL shortening services.

Redirect Caching

A mechanism where browsers or CDNs store redirect responses for a set period, skipping origin server queries on subsequent access.

Client-Side Redirect

A redirect executed by the browser using HTML meta tags or JavaScript, after the initial page has been partially loaded.

Redirect Latency

The delay incurred during a shortened URL's redirect process. A critical performance metric that directly affects user experience and conversion rates.

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FAQ

How should TTL values be configured?

Use short TTLs (300–3,600 seconds) for frequently changing records and long TTLs (86,400 seconds or more) for stable records. Lower the TTL before a DNS migration so changes propagate quickly.

What problems can a TTL that's too short cause?

It increases DNS query frequency, leading to higher name resolution latency and greater server load. A TTL of at least 3,600 seconds (1 hour) is recommended for normal operations.

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