Mux: video that plays before it is processed

The usual video pipeline transcodes every rendition before anyone can watch: queue a job, wait, publish. Mux reversed the order. An upload is cut into short segments, and a segment is transcoded when a viewer first asks for it, streamed out as it is produced. A long file can play within seconds, and renditions nobody watches are never made.

That moves work out of a batch queue and into the request path, which changes what can go wrong. Mux's write-up of a 22-day storage incident shows it well: corrupted segments came from a cancelled read that affected other readers of the same file, a race between deleting and replicating, and incomplete writes treated as complete files, all made worse by a scaling change that slowed object storage during bursts. None of these is exotic. Each is a small assumption that held until the load changed.

Read them next to the video pipeline investigation, which builds the conventional queue-and-workers design. Just-in-time transcoding is the alternative when time to first play matters more than predictable batch cost.