TTL (time to live) is the cache lifetime set on an object - how long an edge may keep serving it before checking with the origin for a newer version. It is configured via cache-control headers and is the lever that balances freshness against offload.
For immutable VOD segments, long TTLs are ideal: the bytes never change, so they should stay cached for a long time, maximizing cache-hit ratio. For live manifests that update every few seconds, TTLs must be very short or the player will see stale content. Getting TTLs right per object type - long for media, short for manifests - is fundamental to both correctness and cost.
The handbook · 7 volumes
Fora Soft Video Engineering Handbook
TTL balances freshness against cache offload: long for immutable VOD segments, short for live playlists that change every few seconds. We wrote seven volumes covering the video stack; for TTL settings start with Volume 3 on CDNs and caching, then Volume 2 on live manifests and segment delivery, with encoding in Volume 1. Written by Nikolay Sapunov, CEO at Fora Soft.
Live playlists going stale or VOD segments hitting origin too often?
We will review your cache headers and CDN logs and send TTL settings per object type with the expected offload. 250+ video products shipped since 2005.
