Prime Video HLD: The Transcoding Pipeline Behind Streaming Video

When you hit play on Prime Video, the file you stream was never uploaded in that form. A studio handed the service one giant master file; before anyone could watch it, the platform had to chop it into short segments and re-encode every segment into a whole ladder of qualities — 240p for a phone on the subway, 1080p for a TV on fibre. That preparation step, transcoding, is a massive parallel-jobs problem, and the clever part is that you don't have to wait for all of it: a quality becomes playable the moment its own segments are done, so streaming can start while the higher rungs are still encod…