Ttl

https://www.cloudflare.com/learning/cdn/glossary/time-to-live-ttl/ (opens in a new tab)

Time To Live (Caching)

Time to live (TTL) refers to the amount of time or “hops” that a packet is set to exist inside a network before being discarded by a router.

For CDN cache,

determine how long cached content should be served from a CDN edge server before a new copy will be fetched from an origin server

For DNS cache,

determines how long a DNS cache server can serve a DNS record before reaching out to the authoritative DNS server and getting a new copy of the record