In our ongoing effort to enhance live streaming efficiency and viewer experience, we at TikTok partnered with CDN77 to explore a new approach called “Media First” This talk will examine how Media First transforms segment-based video delivery by merging multiple CMAF chunks into unified media objects and leveraging intelligent CDN edge logic. By combining media segments and applying dynamic URL rewriting at the edge, the CDN ensures that each viewer receives the freshest and most cacheable version of the video, even under real-time constraints. By shifting cache logic from “manifest-first” to “media-first,” we observed significant improvements in cache hit ratio, startup time, and stream stability. Specifically, we reduced origin fetches during peak events, improved playback startup predictability across diverse network conditions, and achieved a 2.5% reduction in first-frame delay and a 9% reduction in stalling. This talk highlights the architectural and operational collaboration between TikTok and CDN77 engineering teams, including lessons learned from edge compute deployments, manifest adaptation, and adaptive delivery strategies. Key Takeaways: Media First Architecture: How merging segment groups and rethinking cache hierarchy enables higher media availability and CDN efficiency. Edge URL Rewriting: How real-time request rewriting delivers the most current media while minimizing origin MISS traffic. Performance Gains: Insights into how Media First improves QoE metrics, including startup latency, resolution stability, and playback resilience. Cross-Team Innovation: Lessons from collaborative development between application logic and CDN infrastructure to advance live streaming capabilities. This talk will be co-presented by engineers from both companies and will include real-world production metrics and implementation details. This talk was presented at Demuxed 2025 in London, a conference by and for engineers working in video. Every year we host a conference with lots of great new talks like this – learn more at https://demuxed.com