Caching Strategies for Video Streaming

The Role of Caching in Streaming

Caching is a key technology for improving streaming performance and reducing bandwidth costs. A well-designed caching strategy can significantly reduce origin server load, improve playback smoothness, and lower CDN costs.

Multi-Tier Caching Architecture

A typical streaming cache architecture includes three tiers: browser cache, CDN edge cache, and CDN mid-tier cache. Browser cache lives on the user's device, CDN edge cache is closest to the user, and CDN mid-tier cache connects edge nodes to the origin server.

M3U8 playlist files need short cache durations (typically 2–10 seconds) to ensure timely updates. TS segment files can have much longer cache durations (typically 24+ hours) since segment content doesn't change.

Cache Control Strategies

HTTP cache headers are the primary means of controlling caching behavior. The Cache-Control max-age directive sets the cache expiration time, while s-maxage specifically controls CDN cache time. For live scenarios, playlists use no-cache or short max-age, while segments use long max-age.

Prefetching is a proactive caching strategy where the player requests upcoming segments while playing the current one, ensuring segments are already cached at the CDN edge when needed.

Cache Invalidation and Updates

When video content is updated, old caches need to be invalidated. Common methods include: versioned URLs (adding version numbers to URLs), actively purging CDN caches, and using short cache durations to let caches expire naturally.

For on-demand content that doesn't change, you can set extremely long cache durations or even permanent caching. For live content, playlist caches need more frequent updates.